Reprinted from BRITTONIA, Vol. 16, No. 3, July, 1964

POLLEN MORPHOLOGY AND EVOLUTION OF SARCOLAENACEAE (CHLAENACEAE)1

SlIKKWIN ('ARLQUIST Claremonl Graduate School Mini Raiiclio Santa Ana Botanic Harden, riarcnioiit, California

Tin- family Sareolaenaeeae (correctly named by Caruel 1881), still known in most literature as Chlaenaceae, is endemic to Madagascar. The systematic position of Sareolaenaeeae is not entirely clear. When he described the family, • In Petit Thouars (180f>) claimed the group was allied to Malvaceae or Tiliaceae. This view has been accepted by subsequent French authors. Gerard (1919) em­ phasizes malvalean relationship for the family, although be suggests many simi­ larities with Theaceae as well. Cavaco (1952b) believes that Sareolaenaeeae are polyphyletie. derived from origins near Theaceae and Tiliaceae, respectively. Cavaco does not outline, however, which portions of Sareolaenaeeae might be re­ lated to Theaceae and which might have affinities to Tiliaceae. Dehay's (1957) petiolar Studies emphasize a relationship to Malvales in general and Tiliaceae in particular. Hutchinson (1959) places Sareolaenaeeae in Ochnales, along with Ochnaceae. Scytopetalaceae, Dipterocarpaceae, Ancistrocladaeeae, and a family based on the Madagascar endemic Rhopatocarpugf Sphaerosepalaceae. These views i'ii relationship seem quite various. There may be. however, some degree of affinity, or at least many common features among the putatively-related families mentioned above. Erdtman (1952. 1954) notes similarity between pollen of Sareolaenaeeae and such varied groups as Ericaceae, Caryocaraceae, KidiHn/cra, and Leeythidaceae-Planchonioideae, however. Pollen tetrads of Sareolaenaeeae are of interest not only for the information they may give regarding the relationships of the family, but also as an example iif pollen evolution. These tetrads, in fact, offer examples of some of the most intricate pollen construction to be found in angiosperms. This complexity results not only from the peculiar ways in which external sculpturing conforms to the tetrad as a whole, but also the truly remarkable ways in which the internal walls of the tetrad are sculptured. Had sectioned material not been employed for this study, these latter phenomena and their rich variety would have gone unnoticed. These results emphasize the need for study of sectioned material, whether very thin sections viewed by light microscopy or ultra-thin sections studied by elec­ tron microscopy, for further advances in pollen morphology. Our knowledge of tetrads and pollinhi especially should benefit from study of sections. The pollenmorphologieal data herein are valuable for comparison with taxo- nomic systems within the family, and correlations are discussed in the conclusion of this paper. The only previous monographic survey of pollen of Sareolaenaeeae is that of Smith (1934). Smith claims that all but two of the genera for which he bad material have not merely tetrads, but groups of lii grains united into "tetra- quartets." This was refuted by the data of Erdtman (1945, 1952, 1954). When viewed in ordinary whole-mount preparations, the complicated optical appear­ ances of external and internal walls and surfaces make interpretation difficult. Therefore, paraffin sections were employed in the present study. This technique quickly revealed that all Sareolaenaeeae have only tetrads, never larger aggrega­ tions, but more importantly, the exine stratification of external walls and the

'Tliis investigation WW aided by two grants from the California Research Corporation. BRITTONIA 16: 231-254. Jul L964, 23] 232 BRITT0N1A [VOL. 16 sculpture and stratification of internal walls could be examined. The unusually good representation of the family at my disposal and the richness of sculptural detail revealed in these preparations compelled production of this study. Pollen of all of the genera and. with but few exceptions, the known species of the family was available for study. Unfortunately, no living or liquid-fixed material, which would certainly be desirable for certain future studies, was available.

MATEBIALS AND METHODS The basis for this study was material collected from herbarium specimens in the United States and Europe. The writer wishes to thank the curators of the herbaria cited in Table 1 for their generosity in sharing this material. Dr. Peter Raven secured the material from European herbaria, and deserves special thanks for this task and for encouraging this study. Anthers containing pollen were treated with a warm 2..V, aqueous NaOH solution until cleared and expanded. These anthers were washed, and each col­ lection was separated into two portions. One pact was dehydrated in a tertiary butyl alcohol series and infiltrated according to Johansen's (1940) schedule, sec­ tioned at 5 ft and stained with safranin. The other portion was dehydrated in an ethyl alcohol series, stained with safranin in absolute alcohol, destained, and transferred to xylene; these anthers were crushed in a drop of eanada balsam on a slide, and permanent whole-mounts of tetrads were thus prepared. The NaOH technique proved satisfactory because various degrees of treatment could accomplish good clearing and expansion to normal size without appreciable altera­ tion of exine or. in many cases, destruction of intine. In addition to XaOH- treated material, untreated tetrads were removed from dried specimens and mounted directly in glycerine. These provided comparisons to insure that intine and exine structure seen in the XaOII-treated material did not reflect degrada­ tion from the NaOH treatment. Analysis of the tetrads was based mostly upon sectioned material viewed under oil immersion with critical illumination. External appearances of tetrads and their dimensions wen- obtained from whole mounts. Dimensions given in Table 1 correspond to a measurement, taken vertically, of the widest point of the first figure on each plate of drawings. Drawings were prepared with the add of a microscope projection device and by means of direct observation. Specimens studied are designated in Table 1. and are not indicated on legends for figures unless more than one collection of a species was available for study. Measure­ ments of tetrads arc based on 100 tetrads, except for those specimens which did not provide 100 tetrads. Terminology for pollen structure follows that of Erdt- man (1952). Tetrads are tetrahedral in organization, except for Schizolaena exinvolttcrata, S. parviflora (Erdtman 1954) and 8. viscosa (fig. 20-2-'> | in which both tetra­ hedral and variant types are found. Each grain of a tetrad has three apertures, arranged in accordance with Fischer's law (cf. Erdtman 1952). Adjacent pairs of apertures, however, are united into common apertures (seen in the second figure of each plate of drawings, center). Various types of views and sections are used in this study to reveal fully the complex detail of the tetrads. For each specie-, illustrated, a view of a tetrad from directly above a common aperture of one of the grains an 1 a view from directly above a pole of one of the grains are shown. A section of a tetrad, show­ ing a wall in face view for one of the grains is also drawn. Often, such a section also shows a loiiL'isection of a pair of apertures (eg., fig. 13. 4.5). The thickened 1964] CARLQUIST : SARCOLAEXACEAE POLLEN 233

ring of nexine is usually best illustrated in a section just above or below the internal wall. On account of the pit- or channel-like structures, a transection of an internal wall, tangential to an aperture, is useful and is figured for all species. Sections of external walls are drawn to show the nature of sexine orna­ mentation and for most species illustrated a surface view of sexine ornamenta­ tion is given. Conventions used in drawings are: stippled = nexine; black = sexine (except in fig. 53, where it is stippled) ; white = an additional (ectosexine) layer present in some genera (viz, fig. 89) ; intine = a pair of parallel dotted lines shown at apertures in some figures (e.g., fig. 80) ; a single dotted line across an aperture indicates the bulging germ pore, for which the precise thickness of intine could not be reliably determined. The optical distinctions between these layers may be due more to sculpture than to chemistry or refractiveness, as Chambers and Godwin (1961) and others have claimed for various families. Nevertheless these layers may represent sequential events in formation of the wall, and provide stratification which can be compared from genus to genus, although such correlations are sometimes difficult and, as with any study of complex wall stratification, assignment of terms to particular wall layers is to some extent provisional. Thick intine (5 /x in thickness) was observed covering germ pores in Lepto- laena bojeriana, Ehodolaena altirola, and Sarcolaena grandiflora (fig. 80). This thick intine narrows sharply toward the interior of the grain. Intine was identi­ fied not only by position but also by the marked difference in staining reaction between exine and intine. "With respect to taxonomic nomenclature, the recent monograph of Cavaco (1952a), which appears supported by evidence from pollen, is followed.

DESCRIPTIONS Schizolaena.—The simplest, as well as the smallest, tetrads in the family are those of Schizolaena (fig. 11-23). Grains are altered in shape as a result of mutual contact in the permanently-united tetrad but are otherwise of a rounded shape (fig. 11, 12). The common apertures have a nearly circular outline, with the internal wall dividing the circle (fig. 12). The appearance of ellipsoid com­ mon apertures in Erdtman's (1954) figures of Schizolaena may be at least, partly due to perspective, for apertures shown in face view appear nearly circular. The internal wall, where it faces the common aperture, is thickened (fig. 13, 15). The ronformation of thickenings of walls around the aperture (fig. 15) suggests that these thickenings might serve as a closure device for dehydrated grains. I have observed similar thickenings in permanently-united tetrads in other families, such as those of Vacciniuni oration (Ericaceae). This is probably a parallelism, rather than an indication of relationship. The alteration of the internal wall with relation to the tetrad habit and the conformation of the common apertures suggest that Schizolaena tetrads, the least specialized in the family, are already evolved as units and are more firmly united than tetrads in certain other families (e.g., Onagraeeae). Smith (1934) reports that tetrads of Schizolaena cauliftora and •'>'. ("Rhorfola-f na"| parviflora are "rather easily separated." Smith does not detail his method of preparation. The present study definitely does not confirm Smith's observations, which might have been the result of viewing aberrant or immature tetrads. The only species in which a large number of aberrant tetrads was observed was 8, riscosa (fig. 20-23). In the collection studied, no perfectly formed tetra­ iled ral tetrads were observed. Most tetrahedral tetrads appeared at least slightly 2U4 BRITTONIA [VOL. 16

Fn;. 1 in. Microtome sections of pollen tetrads of Sareolaenaeeae. PM. 1. Erema rotundifolia. Section showing longitudinal Lection of germ pore (upper left); tetrad at right shows wall thickened between an adjacent pair of grains. Fn;. _. Pentcchlaena latifoHa, Sec­ tion showing :i pair of germ spores emerging from the common aperture; note thickening of wall between grains. Fi<;. 3, 4. Leptolaena bojeriana, Baron. IS?.!. Fn;. :'.. Section of tetrad Showing one of the internal walls in face view; note the tongue-like extension of this wall toward the aperture and rlie pair of channel-like thickenings in the wall (see fig. 64, (>7 I. Fia. 4. ton tangential to a common aperture, showing a sectional view of the wall between a pair of grains. The central thickening is the tongue-like portion of the wall (see tig. 6ft, 68 Fn;. f>, »>. Leptolaena mvltiflora. This pair of sections corresponds with those of tig. 3, *. respectively. The internal wall between the two grains has a complete rif't. Fn;. 7. li'lioilolaena iillirula. Section corresponding to those in figs. 3, 5. In the wall shown in face view, thickened 1964] CARLQIIST : SARCOLAEXACEAE POLLEN 235

TABLE 1. Diameter of Species (olloetion tetrad, M Eremolaena huinblotiium Baillon Perrier de la B&thie 14759 (K) 101 /•.. rotuntlifolia (Gerard) Danguy Capuran 9164 (P) 79 Leptolaena, subg. Leptolaena: Blackburn I B 94 /,. multiflora du Petit Thouars Humbert 5955 (US) 90 /.. i«i ttriflora Baker Eumbert 7111 (K) 70 L. pauciflora var. tnrbinata (Baker) H. Perrier Elliott 8178 I B i 65 Leptolaena, sabg. XeroeKtamys: Bnmbert 5864 I B 73 I,, iir- naria (Gerard) Cavaco Terrier de la Bathie 3030 (BM 71 /.. boj> riana (Baillon) Cavnco Baron 1873 (K) 77 /-. diospyroidea (Baillon I Cavaco Baron 5112 (B 78 /'. ntmlihuna latifolia II. IVrrier Perrier de la Bathie 1248 (P) 91 Perrierodendron boinense (H. Perrier) Cavaco Perrier de la Battue 18479 ( K 88 Rhodolaena altiniia du Petit Thenars Perrier de la Bathie 1644 (K) 66 B. bdherkma Baillon is 808371 95 /.'. luii/iblotii Baillon Hildel.ran.lt 3823 (BM) 88 Surcithi' na codonochlamys Baker Bumblol 428 B i LOO 8. dt Ipiiiii' nsix ilu Petit Thouars I )cca rv 2221 (IS !Hi iophoradn Petit Thouars Somber! 50886 (K) 101 8. artiltdiflora du Petit Thouars du Petit Thouars in 1919 (P) 85 8. multiflora du Petit Thouars .1. v. Thompson (BM) M 8, oblongifolia Gerard Baron 6380 (BM i 104 Schi^olaena cauUflora du Petit Thouars Humbert 5996 (GB I B8 8. i•.nm-olucrata Baker Perrier de la Bathie 13575 (K) 100 8. lamina Baillon • lu Petit Thoaara 1876 (BM) 13 8. parviflora (Gerard) H. Perrier ird I K 38 8. rosea du Petit Thouars Perrier de la B&thie 13268 (P) tt S. viwo.sa Gerard Decary 966 (P) 43 Xyloolaena perrieti Gerard Service Forest. 19190 (P) 50 X. richardii Baillon I'.a inn (K) 48* Perrier de la Bathie 3018 (P) 103 Perrier de la Bathie 1.1424 (BM) 112 -Xorinal tet rahedral tetrads only; decussate tetrads, 54/*; planar tetrads 60/». asymmetries] (fig. 20). Elongation of a pair of grains results in the appearance shown in fig. '22. Reorganization of the four grains characterizes a few tetrads, varying from a decussate form shown in fi

FIG. 11-23. Pollen tetrads of Schizolaena. FIG. 11-17. >'. mvii. FIG. 11. View show­ ing tetrad seen from pole of one of the grains. FIG. 12. A'iew of tetrad seen from above a common aperture. FIG. 13. Section showing internal wall in face view (left; darker stippling indicates thickening of wall near aperture: portion of tetrad at right shows internal wall in median section; note thickening of wall near aperture, germ pore for each protoplast. FIG 14. Wall in sectional view, enlarged. FIG. 15. Portion of apertural region (viz, fig. 13, right) enlarged. FIG. 16-17. Two views of exine surface, enlarged. FIG. 16 is at a lower level. showing pores in sexine; fig. 17 shows that many of these pores are closed over at a higher level (nearer the outer surface); compare with sectional view, fig. 14. FIG. 18-19. Schizolaena puniflora. FIG. 18. External wall in sectional view. FIG. 19. Exine in face view; sculpturing consists of rods, some of which are laterally joined. FIG. 20-23. Schizola> no viscosa. FIG. 20. N' ir-iiornial tetrahedral tetrad. FiG. 21. Tetrad slightly altered from the tetrahedral arrange­ ment. FIG. 22. A tetrad in which one pair of the grains is elongate. FIG. 23. Tetrad in which the four grains are arranged in a plane. Fig. 11-13, 20-23, X 620 (bracket = 50 n, applies to these figures). Fig. 14-19, X 1800.

Schizolat na is noteworthy in the absence of observable sexine elements within internal walls. This would support interpretation of Sckizola* na tetrads as firmly- united and therefore specialized. Sections revealed firm union of grains, the line between nexine of adjacent grains not easily visible. Eremolaena.—The two species. E. rotundifolia (fig. 24—:il and M. humbloti- ana (fig. 32-38) are quite different and are discussed separately. Eremolaena rotundifolia shows specializations fewer than in the remainder 1964] CARLQUIST: 8ABCOLABNACBAE POLLEN 237

FIG. 24-31. Pollen tetrads of Bremotaena rotundifolia. Via. 24. View of tetrad from pole of one of the grains. A pair of low ridges accompanies each of the common apertures. FIG. 25. Tetrad as seen when common :ipi-rture is in face view. FIG. 26. Section of tetrad; internal wall in Caee view. above. A shallow indentation is present in this w.i 11 internal to the common aperture. Absence of sexine in places between adjacent walls creates the appearance of irregular pita in the internal wall seen in face view. Fi

of the family, with the possible exception of Schizolaena. The outlines of the four grains in the tetrad are clear (fig. 24-2(ii. but the outline of each grain is related to the rounded shape of the tetrad as a whole. The common apertures are nearly circular in outline, but are accompanied by ridges, formed of thicker sexine material, which run toward the poles of ihe grains and fade out distally from the apertures. A transection of such a ridge is seen in fig. 2!'. These pairs of ridges are reminiscent of eolpi, and might be interpreted as that, but one would expect the simpler tetrads of Scliizolnc.na to have eolpi also if this is a 238 BRITTONIA [VOL. 1G vestigial feature in Eremohu na rotundifolta. As mentioned elsewhere, the pres­ ent study fails to confirm presence of true colpi in Sareolaenaeeae. As in Srlii:i/Jatiia. the portion of the internal wall adjacent to the common aperture is thickened (fig. 1, 30, 31). This wall is often indented at this location (fig. 26). Sexine elements are relatively large and flake-like (fig. 27). They may be perforated by lacunae. These flakes appear to join with each other toward the exterior surface of the grain (fig. 28; see also in sectional view, fig. 29). Sexine elements are present between grains (fig. 30, 31). In addition to the larger sexine elements forming ridges behind common apertures, ornamentation is grosser along the points of juncture of the grains (fig. 31, left and right). A few sexine ornaments are present along the edge of the external walls facing apertures (fig. 1. 30). Sexine between internal walls is lacunose, and the outlines shown in fig. 26 and 29 (below) are to indicate these lacunae. Nexine is thicker around the common aperture (fig. 29, upper right). In all parts of the tetrad, nexine tends to be spongy or lacunose, especially in thicker areas (fig. 29, 30, 31). Nexine along internal walls may be of uneven thickness (fig. 2(1 above). Eremolaena kumblotiana (fig. 32-38) is different from E. rotundifolia in many respeets. The shape of the tetrads is similar, but the tines separating the grains are more obscure in E. kumblotiana, and tetrads are larger. Sexine is present not as a series of low flakes but as ridges of large lumps. These ridges run in pairs beside the common apertures, a much more pronounced feature than the surface ornamentation of E. r&timdif&Ua. These ridires meet at the pole of each grain (fig. 32, center), but are intercontinuous. A small island of sexine lumps is present at this junction. Sexine is present on internal walls between grains (fig. 37, 38). Lacunae in this layer are indicated on the facing wall in fig. 34. At the common apertures, a recurved nexine flange bears sexine lumps (fig. 34, top). These lumps extend down into the rift internal to the common aperture. Lacunae are present in the sexine lumps i fig. 34-36). The contours of these lacunae suggest that successive layers over earlier-formed lumps or droplets were involved in their formation. Nexine is thicker near the apertures, forming a ring (fig. 33, center; fig. 36). A rift internal to the common apertures forms a complete break (excepl pre­ sumably for a thin intine layer) in the internal walls, so that the four cells of tetrad can be in contact. If intine is not present at this point, protoplasts could be intercontinuous along these rifts. Along each rift or channel, there are two pairs of nexine borders laid down upon the nexine of the walls. These layers may thus be termed endonexine. They may take various forms (fig. 37, 38), but are invariably quite wide. As in E. rot it >i<1ifolia, nexine tends to be highly spongy in nature where thickest (fig. 34-38). The significance of the peculiar rifts in the internal walls is discussed in a later section. Perrierodendron.—The single species, P. bomense (fig. £9-53 was formerly included in Eremolaena. Although the two species of Eremolaena described above are remarkably divergent, pollen tetrads of Perrier&denSron are distinc­ tive enough to support generic segregation. The tetrads are rather small, and the outlines of the component grains are clear (fig. 39-40). Major sexine elements are restricted to pairs of bands or ridges which run from the common apertures to the poles. Most of these ridges form closed rectangles, as shown in fig. 40 (center) and fig. 44. Some of the ridges may join at the pole of a grain, and 1964] CARLQUIST : SARCOLAENACEAE POLLEN 239

FIG. 32-38. Eremolacna humblotiana. FIG. 32. Tetrad seen from above pole of a grain. The ridges beside the apertures are intercontinuous, forming large triangular outlines, each of which encompasses portions of three of the grains. "Islands" of sexine lumps occur at poles of grains. FIG. 33. View of tetrad from above one of the common apertures. The broken lines indicate the ring of thickened nexine inside the aperture and, right and left, portions of an internal wall which is thickened near the aperture (corresponding to the thickenings shown in fig. 37, 38). FIG. 34. Section of tetrad; internal wall in face view, above. Between the wall thickenings, a rift is present. Xo wall material is present in the center of the tetrad. The lower portion of the tetrad corresponds to a section at right angles to the upper portion. FIG. 35. Enlarged portion of wall adjacent to aperture, as in fig. 35. Note spongy nature of nexine. FIG. 36. Section just below the level of that shown in fig. 35, showing portion of the thickened nexine ring seen in face view in fig. 33. FIG. 37, 38. Sections of halves of walls separating adjacent grains, showing the peculiar nexine thickenings which accompany the rift. Fig. 32-34, X 620; Fig. 35-38, X 1800. 240 BRITTONIA [VOL. 16

FIG. .39-53. Perrit rod&uhron boineu.se. Fig. 39. View of tetr.nl seen from above pole of a grain. The ridges form closed loops where they approach each other in the center. Fits. 4". Tetrad viewed from above one of the common apertures. FIG. 41-43. Variations in the r which meet at poles of grains. FIG. 41. Two pairs of ridges are interconnected. FIG. 42. All three pairs of ridges are intercontinuous. FlG. 43. Like tig. 42, but an island-like loop is formed by one of the ridges. FIG. 44. Ridge-loop like that shown in face view in fig. 40, showing sexine lumps present within the loop. FlG. 45. View of tetrad in section. Pair of germ pores at right, Avail in face view at left. Pitted appearance of wall, left, due to absence of sexine in irregular areas in center of internal walls. FIG. 46. Enlargement of area at right, fig. 45. FlG. 47. View of section of aperture, like th.it shown at left, rig. 45. hut at a slightly higher level, showing conformation of sexine and nexine. FIG. 48. Section of internal wall where a pit like thickened area occurs, homologous to those shown in figs. 67, 92, and 104. FIG. 49. Section tangential to aperture, showing thickening of wall just inside aperture (viz, fig. 45, right). FIG. 50, 51. Sectional view corresponding to center of fig. 49, showing varia­ tions of sexine in thickened areas. FIG. 52. Enlarged section corresponding to fig. 45, upper left, at juncture- of pollen grains. FlG. 53. Low mound-like ornaments, which often beat a hole centrally, seen in face view. Fig. 39-45, 49, X 620. Fig. 46-48, 50-53, X 1800. such alternative conditions are .shown in fig. 41-43. There is a tendency in a few instances to form an island of sexine material in the center of such a juncture (fig. 43). Such conformations may help to explain the origin of intercontinuous ridges and grooves, as in Leptolaena, Xyloolacna, etc., in which a triangular 1964] CARLQUIST: SARCOLAEXAt EAE POLLEN 241

"island" is formed at the pole of each grain. Occasionally, lumps of sexine mate­ rial may occur within the pairs of ridges (fig. 44). The ridges consist of a series of flattened lumps, and these lumps are fused at the edge of the ridge away from the aperture. The united edge of the ridges overarches the base (fig. 45, 47. 49) and at the common apertures, sexine elements may extend down into the aperture (fig. 47, center). No lacunae were observed in the sexine lumps. In addition to the ridges, sexine is presenl as small low patches on the outer surface of the tetrad near the lines of juncture of the grains (fig. 45; in detail, fig. 52, 53). These lumps are very thin and may be regarded as a continuation of the sexine which interconnects -rains in internal walls. The low lumps of sexine are often perforated and thus appear crater-like (fig. 52, 53). Lacunae are also present in the sexine of internal walls (fig. 46, 48, 50). These lacunae appear irregular in face view (fig. 45, left). The internal walls are thickened where they face common apertures (fig. 41. 46). Such thickening is shown in sectional view in figs. 49-51. Sometimes the sexine within these thickenings appears to be in droplets (fig. 51). and other sections suggest a double series of lacunae, corresponding to each of the adjacent grains. In addition to the thickenings related directly to apertures, pit-like thick­ enings containing a gap in sexine (fig. 48) occur in positions homologous to those shown in fig. 99, center. Nexine is thicker near apertures in both external and internal walls (fig. 46. 50, 51). A thickened ring of nexine around the common apertures (fig. 47) ap­ pears, at least in some places, to be an addition within, and overhanging, the thin outer layer of nexine. No sponginess of nexine was observed. The internal wall facing the aperture may have a slight rift or indentation (fig. 45, left). Nevertheless, contact among the protoplasts or intine-covered germ pores of the four grains must be minimal. Pentachlaena.—With respect to external appearance, the single species, P. latifolia (fig. 2. 54-60) has tetrads which resemble those of En nmlm na liiim- blotiana. The pattern of inten-ontinuous ridges composed of large lumps of sexine material (fig. 2. 54-60) is similar, as are the '•islands*' of such lumps near the poles of each grain (fig. 54. center: fig. 55, top and bottom). The outlines of each grain are evident, for as in Schizolat na. each grain is rounded in shape. The sexine lumps are somewhat flattened by mutual compression (fig. 54. •}•)). Care­ ful study reveals that they contain lacunae (fig. 57, above; fig. 60). Drop-like lumps of sexine in which lacunae were not observed occur within internal walls (fig. 56-59). Large spaces between these lumps, shown photographically in fig. 2. are nut indicated in the facing wall, fig. 58, except where the rift in the nexine occurs. This rift runs inward from the common aperture (fig. 58; fig. 59, below i. The portion of a section shown in fig. 57 represents a section to one side of this rift. Pit-like thickenings, homologous to those in fig. 99, center, may or may not be present (fig. 2, left; fig. 56, left of center, above and below). Nexine is thicker near the common apertures (fig. 2, 56, 57). Nexine may be perforated by numer­ ous lacunae, or spongy in appearance (fig. 56, 57, 60). The center of the tetrad may contain a broad area of sexine droplets or lumps (fig. 58). Leptolaena—Like Sarcolaena, Xyloolacna, and Rhodolacna, Leptolaena (in­ cluding Xerochlamys) shows a much more specialized structure than do the genera described above. Two species, representing the subgenera XerochJamus and Leptolaena respectively, are illustrated here: L. bojeriana (fig. 3, 4, 61-70) and L. multiftora (fig. 5, b'. 71-77). In L. bojeriana, no pilum or lump-like sexine 242 BRITTOKIA [VOL. 16

FIG. .">4 60. Pentachlaena hit \ folia. FIG. 54. View of tetrad from above pole oil a grain. FIG. ">.">. \ ii ,v nf tetrad from above one of the common apertures. Note superficial similarity In ligs. 32, 33. FIG. 56. Section of tetrad; a pair of germ tubes emerges from the common Aperture at right. FIG. 57. Enlarged view of same, showing porous nature of sexine orna­ ments, presence of sexine elements between walls of adjacent grains, and spong} nature of nexine. FIG. •">*. Section of part of tetrad, showing internal wall in face view. Split in nixiiic running inward from aperture reveals sexine elements of the interna] wall. Fn;. 59. Section Of tetrad tangential to aperture, showing the thickening of tin internal wall interior to the aperture. FIG. (SO. Section of apertural region, higher than tin- level shewn in tig. 58, showing the nexiiif thickening beneath the two ridges of sexine elements, which are markedly taeui FIG. r,4 -58, 58 59, X 620; FIG. 57, 60, X 1800. elements are viable superficially. However, paired ridges, related to the inon apertures, are evident. The outlines of these ridges form shield-shaped areas; there are lour of these (e.y:.. fitr. 61, below, is one) and each encloses portions of three adjacent grains. These three lobes are not to be interpreted as three entire 1964] CARLQIIST: SAECOLAENAOBAE POLLEN 243

Fn;. 61 70. Leptolaena bojeriana, Baron 1878. FIG. 61. View of tetrad from above pole of a grain. FlG. 62. Portion of tetrad, seen from above a common aperture. Broken lines, circle, indicate thickened ring of nezine within aperture; broken lines, right and left, indicate interna] walls separating tetrad grains, tliiekenings along the rift (viz, fig. 69). FlG. 63. Out­ line of grain: ootch in ridge is adjacent to a common aperture. FlG. 64. Seetion of tetrad; interna] wall in face view, above; rift in nexine reveals tongue of thickened sexine (see fig. 69). Where thickened area widens toward center of tetrad, pit- or channel-like structures (fig. 67) are present. Pis. 65, 66. Portions of sections of tetrad at a higher level than that shown in fig. 114. showing thicker la vers at more distal portions of grains. FlG. 65. Point of .juncture of three grains. FlG. 66. Point of juncture of two grains, external surface of tetrad below. FlG. 67. Thickening in wall near center of tetrad (like that, center below, in fig. 64). FlG. 68. Section showing region near aperture, like that shown in fig. 64. top. but at a higher level, Showing, below, the ring of thickened nexine (fig. 62, center). FIG. 69. Section of internal wall tangential to aperture, showing nexine thickenings thinking the rift, which contains a thickened area ol sexine. FlG. 70. View of exine surface, showing sexine rods which are, at left, aggre­ gated BO that a pore-like appearance results. Fig. 61-64, X 620. Fig. 65-70, X 1800.

grains, as Smith (1934) musl have when be claimed 16-grain "tetraquartets" in Leptolaena and other genera. At the pole of each grain, ridges diverge and re­ join I fig. 61, center;, leaving a triangular •"island"* in the center. There is an indentation in the ridges beside the common aperture (fi

with the sculptured layer in the preceding genera, be termed eetosexine, is pres­ ent over the entire surface of the tetrad. This eetosexine, present on external walls, fig. 64) is present on internal walls (fig. 64-67) as well. It is especially thick in some places between the grains (fig. 65). The layer of sexine represented in black, which must be termed endosexine, is thickest in the ridges (fig. 64, 68) and where grains join (fig. 66). A tongue-like thickening of sexine may be present (fig. 3, 64, above; fig. 62, center; in sectional view, fig. 4, 69) or absent internal to apertures in L. bojeriana tetrads. Thicker sexine occurs in the pit­ like structures, three of which are shown near the center of fig. 64 (seen also, v enlarged, in fig. 67). A space is present between nexine and sexine in these thickened areas, which bear a specific relation to the rift (fig. 64, above) and the thickenings along the rift. Analysis of endosexine shows that it may, in , places, be composed of rods (fig. 70, rights, but where thicker, rods are fused, forming an O-L pattern. This O-L pattern characterizes endosexine in internal walls (note minute circles in facing wall, fig. 64, above). Nexine is especially thick in a ring behind the common aperture (fig. 62, center; fig. 68, below). This ring is, in a sense, continued inward as the pair of nexine thickenings beside the rift (fig. 3. 4. 68 . regardless of whether or not the tongue of nexine material is present. These thickened areas of nexine have an irregular surface (fig. 69). Nexine is thick in proximal portions of the grain (fig. 3, center) ; it is often thick, corresponding to the widening of the thickened areas along the rift (fig. 64, center) and includes the pit-like zones. Leptolaena m/tltiflora (fig. 71-77) shows many features different from those described above. Externally, the only major difference is the smaller triangular •island'' at the pole of each grain (fig. 71, center). Analysis of sections reveals a condition much more specialized than that of L. bojeriana. The rifts mternal to common apertures are often complete, as shown in fig. 5. 74. The exine rifts internal to common apertures are often eomplete, as shown in fig. •">. 74. so that the protoplasts of the four grains are either in contact with each other or sepa­ rated from each other by thin intine layers. Close observation of exine stratifi­ cation suggests that the sculptured portion is present only in the ridges (fig. 74), and that other portions are covered with unsculptured eetosexine. This eeto­ sexine is. however, pitted on the outer surface of the tetrad (fig. 76, below). This pitting is shown in face view in fig. 77. Eetosexine is dilated along the rifts (fig. 74, center; fig. 76, above). Endosexine shows an O-L pattern (fig. 75). * Nexine is thicker in a ring behind the common aperture (fig. 72, center) and along the rifts (fig. 5, 6, 74, 76). In these thickened areas, nexine is spongy (fig. 76, above). Nexine on internal walls maj7 be irregular, accounting for the spotted , appearance of the wall seen in face view. fig. 5. With respect to external appearance, small '"inlands" at the poles of grains, like those of L. multiflora. were observed in L. or- naria. L. pauciflora, L. ]>auei- flora var. turbinata, and L. rubella. Intermediate-sized ''islands" were observed in /.. i/i'ispyroidea. A distinct L-0 endosexine pattern was observed in pollen of L. diospyroidea. Lobes of grains (e.g., fig. 71, bottom) are less bulging (like L. oiultiflora) in L, pauciflora, L. pauciflora var. turbinata, and L. rubella, but are more bulging (like L. bojeriana, fig. 61, bottom) in L. arenaria and L. dio- spyroidea. On account of limited material, sections were not available for all species of Leptolaena, but marked nexine thickenings in internal walls along rifts were observed in L. arenaria and L. rubella. Rifts open to the center of the tetrad (e.g., fig. 74, center) were observed in whole mounts of L. rubella tetrads. 1964] CARLQUIST: SARCOLAENACEAE POLLEN 245

FIG. 71-77. Leptolaena muttiflora. FIG. 71. View of tetrad from above pole of grain. FIG. 72. Portion of view of tetrad from above 8 common aperture (broken lines indicate the same features as in iff. 62). Vic 73. Outline of portion of tetrad, as in fig. 63). FIG. 74. Section of tetrad. Xote the prominent rift, resulting in absence of wall material in zones between adjacent grains and in center of the tetrad; darker stippling on wall in face view, i above, indicates the thickening of nexine adjacent to the rift (eompared with lig. 34). FlG. 75. View showing pattern Of thick sexine (endosexine I. such as that beside apcrtnral grooves (black in fig. 74). FIG. 76. Enlarged portion of internal wall between adjacent grains (exterior surface of tetrad below). Xote thick eetosexine, thick spongy nexine adjacent to > rift, (which is understood to be at top of figure). FIG. 77. Surface view of eetosexine (layer left white, bottom of lig. 76) on outer surface of tetrad. FlG. 71-74, X 620; FIG. 75-77, X 1800.

The peculiar "tongue" of sexine described above was found only in /.. bojeriana (Baron 1873). and not even in all tetrads of that collection. In summary, al­ though minor differences among Leptolaenas do oecnr. there is no decisive line between the subgenera Leptolaena and Xerocklamys. So material of Cavaco's subgenus Medusiella {L. bernieri) was available tor study. Sarcolaena.—Tetrads of Sarcohc. na (fig. 7> S."> are not unlike those described for Leptolaena bojeriana. The tetrad is spherical in outline and limits of the component grains are less obvious than in other Sareohc-naceae. The polar "is­ lands" are large, and their tips extend to the common apertures (fig. 78, 79). Ridges are prominent and clearly defined. Internal walls are characterized by a deep rift in the thickened nexine (fig. 80; in section, 6g. 81). A thick eetosexine 246 BRITTONIA [VOL. 10

FIG. 78-85. Sarcolaenn grandiflora, J. V. Thompson. Fie. 78. View of tetrad from above pole of a grain. FiG. 79. Portion of view of tetrad from above a common aperture (con­ ventions as in fig. 62). FIG. 80. Portion of section of tetrad, showing internal wall in face view. As in preceding plates, thickened nexine on either side of the rift internal to the aperture is indicated by denser, stippling; double arc of dotted lines on germ pore Indicates thickness of intine. FIG. 81. Section of tetrad tangential to a common aperture, showing the internal wall and portions of the external walls. Etfft in wall at this level is incomplete, for ectosexine is present between the cells at this point, I'IO. 82. Section of exine near aperture, like top of fig. 80, but at a higher level ami enlarged, showing nexine thickening which forms a ring behind the aperture (fig. 79, center). FIG. 83. A thickening of internal wall near center of tetrad, like those shown in fig. 64, 67, 99, and 104, but not indii on fig. 80; see also fig. 7, center. FIG. 84. Portion of an external wall where it is thinnest. FiG. 85. View of surface of endosexine, showing that sculpturing ((insists „f minute pores. FIG. 78-80, X 620; FIG. 81, X 700; FIG. 82-85, X 1800. is present on the ridges (fig; 82). This ectosexine is also present on the outer surface of the tetrad and between the grams in internal walls. Although the rift in the nexine in internal walls is deep, the ectosexine is continuous across part of this rift (fig. 80, center; in section, fig. 81). Endosexine is very thin (fig. 84 1964] CARLQUIST: SABCOLAENACEAE POLLEN* 247 except beneath ridges (fig. 82) and in the pit-like structures (fig. 83). These pit-like thickenings may or may not be present (they are absent in the section, fig. 80). If present, their locations are the same as shown for Leptola-ena bojeri- ana in fig. 64. Nexine thickening along the rift continues into the center of the tetrad (fig. 80, below). Nexine which forms a thick ring behind the common aperture (fig. 79; in sectional view. fig. 82) has a slightly irregular surface, but was not observed to be spongy in texture. The endosexine as seen in surface view has a very fine O-L pattern. Species of Sarcoid* na other than 8. grandiflora show few differences from the pattern described above for that species. Sareolaena mttltiflora has a tendency toward higher, more conspicuous ridges and a coarser O-L endosexine pattern than illustrated for 8. grandiflora. Xyloolaena.—The external appearance of tetrads of Xyloola' na rivhardii has been carefully described and illustrated by Erdtman (1945, 1952). Except for the prominence of ridges, which appears greater in tetrads I studied than in Erdtman's drawings, his illustration is in accord with my observations. Erdt- nian's description of tetrads of this species, as well as those of other genera (1954) is lacking in details of internal structure, however. Xyloolaena- pi rrieri (fig. 86-87) is similar to X. rickardii in external appear­ ance. The general appearance is not unlike that of Sareolaena, and need not be described in detail. With respect to internal structure. A", richardii (fig. 88-96) shows a rift in nexine in internal walls (fig. 8, 9, 88; in section, fig. 94), but sexine continues across this gap toward the interior of the tetrad. Although not shown in fig. 88. thickened zones (fig. 92) may be present in the positions indi­ cated on fig. 99, center. A space between sexine and nexine occurs in these thickened areas (fig. 92). Unsculptured ectosexine covers the surface of the tetrad (fig. 8, top; fig. 88, 94. 96) and is also present in internal walls between the grains (fig. 92, 94. 95). It is thickest on the ridges, as is the endosexine (fig. 89. 90, 93). Endosexine is present as a thin layer elsewhere in external walls (fig. 96) as well as in internal walls (fig. 95), although it is wider in the ridges (fig. 89, 90, 93) and in the pit-like areas (fig. 92). In sectional view, endosexine is lacunose (fig. 89, 90. 93). Seen from the surface, this lacunose condition proves to be due to spaces—how­ ever curved or Tortuous—between rod-like units, which form an L-0 pattern (fig. 10, 91). Sexine in internal walls (fig. 95) is perforated by minute lacunae, indicated by circles in fig. 88. Nexine forms a prominent thickening in a ring behind the common aperture (fig. 87, center; fig. 89, 90). This nexine is irregular in outline (fig. 90) or perforated by a series of lacunae, making it spongy in texture (fig. 89). With respect to finer structure. A', ptrruri conforms to the pattern described for X. richardii, but has a finer L-0 endosexine pattern. Rhodolaena—Tetrads of Ehodolaena altirola (fig. 97—106) resemble those of Xyloolaena or Sareolaena in general features, and need not be described in detail. The internal walls (fig. 7, below) are characterized by channels, part of which is split as a rift behind the common apertures. As shown in fig. 7, this rift is shallow and does not extend far toward the center of the tetrad. There may be an actual break in the wall, except perhaps for intine (fig. 106) and the discontinuity in sexine, toward the center of the grain, majr be accompanied by a covering of nexine. Thus the rift is converted, toward the center of the grain, into a pair of channels like the pit-like structures described above in other genera (fig. 104). This Y-shaped structure may be seen in fig. 7 and 99. Each of the 248 BRITTOXIA [VOL. 16

FIG. 86 96, Xylookunaj tig. 86-87, X. ; fig. 88-90, X. riehardU, FIG. 86. View of tetrad from above pole of a grain. FIG. 87. Portion of a view of tetrad from ftbi common aperture; conventions aa in rig. (>-j. FIG. 88. Portion of section of tetrad; conven tions as in lig. 80. FIG. 89. Section of apertural region, like that of fig. 88, above, but at a higher level and enlarged; thick nexine is a portion of the ring shown in lig. 87, i : note spongy nature of ncxine. FIG. 90. Section through apertural region, at a level D those indicated in fig. 88 and 89. Nexine is lacunose adjacent to aperture. FIG. 91. Surf i' endosexine, showing rod-like units, separated by -paces which, In a transec­ tion of ixiiu-. III.IN lie variously oriented (fig. 89, 90). Fi<;. !»•_'. Thickening in central part of internal wall, like those shown in fig. 64 and 67, but not indicated on fig. 88. PB Enlarged portion of apertural area (top of fig. 88). showing nature of sculpture. Fn;. <>4. • a of tetrad tangential to aperture, corresponding in orientation to the face view of fig. 87. FIG. 9ij. Enlarged portion of the internal wall, such as is iust below in tig. 94. FIG. 90. Enlarged portion of external wall where it is thinnest, as in the nearby portion of fig. 94. FIG. 86-88, 94, X fig. 89-93, 95, 96, X 1800. pair of channels in the center of the tetrad is continuous with one of such a pair from the other grams. Tims, these structures described above as "thicken­ ings" or "pit-Eke structures" in other genera probably are a portion of, or are 1964J CARLQUIST : SARCOLAEXACEAE POLLEN 249

FIG. 97-107. Bhodolaena altivola. FIG. 97. View of tetrad from above pole of a grain. FIG. 98. Portion of view of tetrad from above a common aperture; conventions as in fig. 62. FIG. 99. Section of tetrad; the level drawn is just above the internal wall, above, the sculpturing of which is therefore indicated in broken lines. FIG. 100. Enlarged portion of external wall where it is thinnest. FIG. 101. Enlarged portion of half of apertural region (fig. 99, top), showing sculpture in nexine layer. FIG. 102. Sectional view of an island in the apertural groove (corresponding to a section, taken horizontally, just above center, of the tetrad in fig. 97), like fig. 99, lower right and left. FIG. 103. Surface view of endosexine of external wall, showing rods in transection. FIG. 104. Enlarged view of thickening or channel, such as shown in fig. 99, center, showing break in sexine layer at this point; center of this area = space. FIG. 105. Section of an area where two grains meet, like that of fig. 99, bottom center, but at a higher level, to show exine stratification. FIG. 106. Enlarged portion of an internal wall, from a section tangential to a common aperture, showing widened spongy nexine adjacent to rift which extends internally from the common aperture. FIG. 107. Surface view of endosexine in internal walls, showing pitted appearance, owing to pores in sexine (see fig. 104, right and left, discontinuities in the black layer). Fig. 97-99, X 620; fig. 100-107, X ca 1800. 250 BRITTONIA [VOL. 16 related to, the rift-like interna] sculpture of the tetrads (note, for example, the similarity of internal walls in fig. 3 and 7). The significance of these structures in internal walls is discussed below. The tetrads of Bhodolaena are covered with unsculptured eetosexine, which is also present in internal walls (fig. 104, 106). Sculptured endosexine is thick in the ridges (fig. 101, 102) but thin in other portions of the external walls (fig. 100). In the ridges and the polar "islands'", endosexine is composed of rods (fig. 101, 102; seen in a section parallel to the surface iu fig. 103). Endosexine in internal walls is lactulose; these lacunae are shown in a face view of Thi- layer in fig. 107. Endosexine is wider where walls join near the ridges (fig. 105), an area which shows the exine stratification very clearly. The thick nexine along the rifts of internal walls (fig. 106) and the thickened ring behind the common aperture (fig. 98, center: seen in section, fig. 101) is laeunose or spongy in texture. The species of Rhodolat na other than R. altirola do not show appreciable dif­ ferences from the pattern described above.

DISCUSSION AND CONCLUSION'S Tendencies in Tetrad Structure The simplest of Sarcolaenaeeous tetrads, those of Schizolafna, show the round­ ed form of individual grains one would expect in relatively unspecialized tetrads. The collections of Schizotttena in the present study give no evidence of colpar structure. Erdtman's (1954) drawings of this genus suggest short colpi; either Erdtman's collections differed from mine in this respect, or else drawing per­ spective in his drawings, or possibly even shrinkage, has exaggerated the length of apertures. If a colpoid or colporate form is ancestral to Sarcolaenaceae, how­ ever, Schizolaena is already specialized in this respect. The common apertures in Schizolaena are specialized with relation to the tetrad habit, as suggested in the thickened external and internal walls around the aperture. Absence of external ornaments (other than the minute sculpture of the sexine) is Schizo- Uuna may be interpreted as an unspecialized condition, however, and no rifts are present in internal walls. Tetrads of Eremolaena rotund if alia are notable for their lack of specializa­ tion. The ridges beside the common apertures might delimit a colporate condi­ tion, might represent vestigial colpi, or they might be merely an innovation, formed by higher sexine elements in these zones. In any case, these ridges are relatively faint and do not extend to the poles of the grains. Sexine elements are almost the same height over the entire grain, as well as in internal walls. surely an unspecialized condition. As in some species of Schizoids na, sexine ele­ ments seem clearly derived from pila or lumps. Dimorphism in sexine elements probably accounts for the ornamentation in Pcrrurodendron tetrads, analogous to dimorphism in elements in pollen grains of other angiosperms. such as Xyridaceae (Carlquist 1960). In Perrierod* ndron. sexine lumps seem exaggerated to form the ridges, but are absent over the re­ mainder of the grains except between grains and externally at places where grains join (fig. 52, 53). The remaining genera of Sarcolaenaceae could be said to lack dimorphism except that sexine in internal walls is often different from that on external walls. To be sure, the large lumps which form the peculiar ridges in Eremolaena humblotiana and Pentaehlaena latifolia may be exaggerations of -exine pila, but they have no smaller counterparts elsewhere on the grain sur­ face externally. 19H4 CARLQUIST : SARCOLAENACEAE POLLEN 251

The remaining genera {Sarcoid* no, LeptolasTia, X ijloolacna, and Rhodohn na I are relatively uniform with respect to external appearance. Ridges are promi­ nent and smooth, and extend to the poles of the grains, leaving a triangular "island" where they rejoin. The thickness of these ridges is due to thicker sexine, which is thin or absent on other portions of the grain. These four genera are specialized in having the unscidptured ectosexine layer over the surface of the tetrad. The smooth surface, sculptured into precise ridges and islands, seems to represent a maximal degree of evolution in morphology with respect to the tetrad, the near-spherical form of which masks the outlines of the component four grains.

Tendencies in Internal Wall Structure The least advanced, or at least, the most simple conditions are demonstrated by Sckizolaena and by Eremoleu na rotundifolia. In these species, a small erosion in the wall behind the aperture and a thiekening in the wall within the aperture are present. A prominent rift, and a marked thickening in the wall within the aperture are present. A prominent rift, and a marked thickening in the wall could be said also to be present in Perrierodendron and Pentachlacna. but these genera are much less specialized with respect to internal wall structure than Xyloolaena and its allies. A conspicuous nexine rift accompanied by thickened nexine margins, but with sexine still separating adjacent grains, occurs in in­ ternal walls of Sareolaena, Xyloolaena. and some species of Leptolaena. A further suggestion of specialization is the complete absence of wall layers (except pre­ sumably for intine) across this rift, as in Eremolaena humblotiona and Rhodo- lat na altivola. Rhodolaena, however, has a rather shallow rift. The farthest de­ gree of specialization in formation of the rift is its continuity into the center of the tetrad, where it joins with the three other rifts, so that no wall material (ex­ cept perhaps for intine is present in the center of the tetrad. This condition was observed in EremolfH na humblotiana and Leptolaena multiftora. What is the significance of the peculiar rifts and their thickened margins, to­ gether with the channel- or pit-like formations associated with them in the center of tetrads' One intriguing explanation which can be suggested is that these phenomena are continuations of the corpus-like external furrows and ridges on the external surfaces of the tetrads. The rifts would correspond to furrows, the thickened nexine areas to ridges. As a suggestive example, one may compare the Y-shaped rift-and-channel formation in internal walls of Rhodolaena altivola tetrads (fig. 7, 99) with the Y-shaped grooves and ridges on the exterior of the tetrad (fig. 98, above and below). This tendency toward similarity in internal and external sculpture in tetrads of a species might be considered as a tendency for the same developmental or morphogenetic factors to operate both on external and internal surfaces of the tetrad during ontogeny of the tetrad. This would not explain, however, why the two species of Lepiolat na illustrated have such different internal sculpture despite similar external appearance. The physio­ logical significance of the complex channels and thickenings such as those shown in fig. 99, center, seems dubious. The production of rifts in exine might offer closer contact or, if not separated by intine, actual intercontinuity among the protoplasts of the grains. Such speculations only emphasize the need for study of living and fixed material, especially tetrads with prominent internal-wall rifts. Sexine patterns seem basically composed of rods in Sarcolaenaceae. In Rho- doUu /ui, which seemingly has specialized tetrads, these rods are clearly visible. Union of such units, producing an O-L, pattern, would have taken place in many Sarcolaenaceae if the separate rods, pila, or bacula are representative of a more 252 BRITTOXIA [VOL. 16 primitive condition. In internal walls, this process of union of sexine elements could be said to be accelerated, because Pentachhn na is the only genus in which individual units may be seen to compose the sexine of internal walls. Tetrads of all genera may be said to be specialized in certain respects. The absence of sexine in internal walls in Schizolaena seems specialized, when one considers that in PentacMaena internal sexine is similar to that of external walls. Other examples could be cited which suggest that rates of evolution for different features of the tetrad are not synchronous, even though one cannot give clear evolutionary explanations of the complex morphology of Sareolaenaeeons tetnuls. I

Taxonomic Distinctions The results of the present study support the taxonomic decisions of Cavaco i (1952a). For example. Cavaco's (1951) segregation of Perri rodendron, which Perrier de la Bathie (1925) described as a species of Eremolaena. seems justified. The reduction of Xeroekiam^fi to a subgenus of Leptolama (Cavaco 1951) also seems advisable, despite the characters cited by Perrier de la Bathie as indicating generic distinction. The marked external similarity of tetrads of Eremolaena humblotiana to those of Pentachlaena hit if "I in is not as curious as it might seem. Perrier de la Bathie (1931) and Cavaco (1951) both emphasize the likenesses among En mola-cna, Pentachlat na and Perri' rod' ndron, and call attention to characters of indument. sepals, and the tendency for flowers to occur in pairs; the pollen tetrads of these genera are at approximately the same level of specialization, at least with reaped to external morphology. The two species of Eremolaena do have very different tetrads. Perrier de la Bathie (1931) does emphasize that Eremolaena humbloii- ana differs from E. rotv/ndifolia by having fleshy white free involucral bracts, biflorous involucres, and longer leaves with short petioles and a nerved lamina. The sum of these differences does not seem compelling enough for generic segre­ gation, even noting the difference in tetrads, for similarity between the two species in other respects seems considerable. Phylogenetic Correlations Analysis of generic criteria in the monographs of Cavaco (1952a. 1952b) and Gerard (1919) show that genera differ by a mosaic of characteristics, difficult to arrange in a phylogenetic sequence. Likewise, Dehay's 11957 study of petiolar anatomy emphasizes the uniformity of the family and lack of generic distinc­ tions in these anatomical respects. Arrangements of genera according lo stamen number, locule number, number of ovules, morphology of disc, number of flowers per involucre, sepal number, inflorescence type or morphology of involucre would all be different, so that most of these features could not, individually, be clues to phylesis within the family. The only feature which appears to correlate well with putative stages in pollen evolution is that of involucre morphology. The peculiar cupulate involucres of Sarcolavna, L< ptolai na and Xyloolat na are doubt­ less specializations. Similarity among involucres in these genera is paralleled by their likeness with respect to pollen morphology. On the other hand, the genera Schizolaena, Eremolaena, Perrieroeh ndron, and Pentachlaena do not have these fleshy or woody cupulate involucres, but seem to show a condition suggest­ ing a pair of bracts modified in various ways but not to the extent of the peculiar cupules of Sarcolaena and its allies. This correlates well with the less specialized pollen tetrads (grains rounded and obvious; sexine elements distinct; no eeto- sexine present) in the four genera. 1964] CARLQriST : SARCOLAENACEAE POLLEN 253

Pollen grains of Rkodolaena are clearly of the Sarrohu na type. Involucres in Rhodolat na are absent, ox nearly so. EhodoUuma lias, instead, sepals which become fleshy ai maturity. This discrepancy in correlation with pollen morph­ ology may be explainable in some way. but division of Sarcolaenaceae into two subfamilies on the bases of pollen and involucres would be premature. Much more information, particularly anatomical and eytologieal, is needed to secure a pic ture of phylesis in the family. Pollination The peculiar morphology of tetrads of Sarcolaenaceae naturally raises the question of the pollination mechanisms involved. Careful search revealed no threads, such as characterize some large tetrads (Ericaceae, Onagraceae). The mechanisms for transport of the large smooth tetrads of, say. Xylo&laena would certainly provide the basis for an interesting study.

Pollenmorphological Relationships of Sarcolaenaceae Pollen tetrads of Sarcolaenaceae are nol easily compared with pollen grains of other families. The wide gamut of specialization within Sarcolaenaceae and the changes in pollen structure related to the let rail habit make comparisons diffi­ cult. Erdtiuan (1952) states that pollen of Sarcolaenaceae '"has some characteris­ tics in common with Caryocar, Ericaceae. Kiclmcijcra and Lecythidaceae-Plancho- nioideae." The similarities with Kielmeyera and Ericaceae may be those of the tetrad habit. Caryocar and Planchonia have single grains which possess ridges and even •"islands'- at poles of grains, and are thus reminiscent of Xyloolaena, etc. The fact that these sculptural features are tln.se of single grains in the two genera named and of tetrads in Sarcolaenaceae would make this comparison a superficial one unless one considers that internal sculpture is a continuation of external sculpture in Sarcolaenaceae. This possibility, suggested above, would make a single grain of the tetrad not unlike a grain of (Uiri/ocar. However, even this probably would be a parallelism, for only in the more .-specialized genera of Sarcolaenaceae does any similarity to the Ga/ryocar-Planchonia type of gross sculpture occur. In a Later paper, Erdtman (1954) claims that "study of pollen morphology in this family (Sarcolaenaceae) strengthens the suspicion that there is a relationship between the ('hlaenaceae and the Ericales." Hnltinan does not provide reasons or examples to support this statement, which appears question­ able in view of the evidence from other disciplines concerning relationships of Sarcolaenaceae. More compelling similarities appear when the finer structure of Sarcolae­ naceae pollen is compared with that of other families. The recent contribution of Chambers and Godwin | l!)(il | on fine structure of pollen in TUia platyphyttos reveals that markedly thickened nexine occurs near apertures in that species and. more significantly, this nexine is laciinose, or. as these authors express it. 'eere- bclloid". Also, the peculiar pattern of sexine described by Chambers and Godwin in TUia correlates rather closely to the nature of perforate Hakes, joining each other externally, which compose the sculptured layer of walls in Eremolacna rotundifolia. The perforated ornaments at .juncture of grains in P< rrit rodt ttdron tetrads (fig. ">:?. 53) are more distantly reminiscent of the THin condition. Tili- aeeae have been, as noted in the introduction to this paper, cited more frequently than any other family as probably related to Sarcolaenaceae. Study of the fine structure of more Tiliaceae and representatives of other families is needed to demonstrate if the peculiarities mentioned are more widespread than present 254 BRITTOXIA [VOL. 16 reports indicate. However, if the resemblance between Tilia and Sareolaenaeeae is indicative of relationship, pollen of Eremolaena rotundifoUa would represent a primitive type for the family with respect to pollen structure. The gross morphology of Eremolaena also suggests it is a genus containing many characters primitive within Sareolaenaeeae. Palynological evidence does not support the suggestion of Cavaco (1952b) thai Sareolaenaeeae have polyphyletic origins. LITERATURE CITED Carlquist, S. I960. Anatomy of tluavana Xyriila.-t-;,.-: dbolboda, Orectantht and dchljfl Mem. N. V. Hot. Gard. 10: 85-117. CanieL T. 1881. Pcnsieri sulla tassinomia botanica. Atti Aca.l. Lincei Mem. s,i. J'i-. Math. Nat. aer. 3, 10: 161-251 (reprinted in Bot. Jalirl.. 5: .">49-616. 1883). Cavaco, A. 1951. Bemarques sur les genres Leptolaena et Xerochlaimis (Chlaenacees). On nouveau genre de Chlaenaceae. Bull. Mus. Nat. Hist. Paris II 23: L33 I •'.'.'. . 1962a. <'lilaenace>s. In Humbert, H., ed., Flore de Madagascar el dea Comores 126: 1-37. . 1952b. Recherches sur les Chlaenacees. fumille enilemique tie Madagascar. Mem, Inst. Bet Madagascar, s£r. B, 4: 59-92. Chambers, T. C, & Godwin, H. 1961. The fine structure of the pollen wall in Tilia plaly- phyllos. New Ph.vtol. 60: 393-399. Dehay, C. 1957. Anatomie eoniparee de la feuille des Chlaenacees. Mem. [nst. 8ei. Madagas­ car, ser. B, 8: 145-203. Erdtman, G. 1945. Pollen morphology and plant taxonomy. V. On the occurrence of tetrads and dyads. Sv. Bot. Tidssk. 39: 286-294. . 1952. Pollen morphology and plant taxonomy. Angiosperms. The Chronica Botanica Co., Wnltliain, Mass. • . 1954. Pollen morphology and plant taxon y in some African plants. Webbia 11: 405 412 (also included in GhraiU 1'alynologica, 1(1), 1954.) Gerard, F. 1919. Etude sy.stemati<|Uc, morphologique rt anatomii[iie des ('lilaenaeees. Thesis. Marseilles. Hutchinson, J. 1959. The families of Severing plants. K<1. 2. Vol. I. Dicotyledons. Claren­ don Press. Oxford. Johansen, D. A. 1940. Plant microtechnique. Median Hill. New York. Perrier de la Bathie, H. 1925. Nouvelles remarques sur les Chlaenacees. Bull. Soc. Bot. Fr. 72: 397-813. . 1931. Remarques sur les Chlaenacees. 2. Bull. Soc. Bot. Fr. 78: 46 65. Petit Thouars, Aubert du. 1805. Histoire des vegetans recuillis dans tea Ilea australes d'Afrique. Levrault, Schoell et Co., Paris. Smith, C. C. 1934. A case of "pollinia." Phytologia 1: 83-88.

RECENT DEATHS OP BOTANISTS.—Members of the Society will learn with regret of the deal lis of the following botanists: Truman G. Yuncker, of DePauw University, long-time student of Cuscuta and of the Piperaeeae and past president of the American Society of Plant TaxonomisK. on January 8, 1964. t Mto Emery Jennings, formerly Professor of Botany, head of the Department of Biological Sciences, University of Pittsburgh, Curator and Director of the Carnegie Museum, Pittsburgh, Pens., on January 2(5. 1964. in Pittsburgh, at the age of 86. Charles Baehni, Director of the Convervatoire et Jardin botaniques, Pro­ fessor of systematic botany at the [driver-site de (ieneve. gracious hosl t<> many American botanists, on January 23, 1964.