J. Indian hot. Soc. 50 : 89-100.

SPORE MORPHOLOGY OF INDIAN FERNS—X : DAVALLIACEAE AND OLEANDRACEAE^

By S a n t h a D evi a n d B. K. N a y a r * National Botanic Gardens, Lucknow

A bstr a c t

Spore morphology is described of 31 species (19 belonging to Araiostegta, Davallia, Davallodes, Gymnogrammitis, Humala and Leucostegia of the Davalliaceae, and 12 to Arihropterix, Nephrolepis and Oleandra of the Oleandra-ceae), based mainly on acetoiysed preparations and supplemented by observations on untreated spores. The spores are of the monolete bilateral type and ranging in average size from 26x45 li to 44x78 (i in the Davalliaceae [more commonly ca. 32x65 i;.) and ra. 20x33 (i in Nephrolepis, 26x35 [i in Oleandra and 32x 43 n in Arihropieris. The exine is 2'5—3 (i thick and commonly subverrucate—areolate to tuberculate in Davalliaceae (granulose in Gymnogrammitis), smooth in Arthrop- leris and Nephrolepis and spinulose in Oleandra. A perine is absent in the Davalliaceae ; in Oleandraceae the spores are perinate. The perine is commonly smooth in Nephrolepis (spinulose in N. undulata), granulose in Arthropteris and spinulose to spinose in Oleandra ; it is closely adherent to the exine (sometimes indistinguishable) in most spccies of Nephrolepis and loose in others. It is concluded that the separation of Davalliaceae and Oleandraceae as two distinct taxa is justified, that Nephrolepis is possibly the more primitive and Oleandra comparatively the most advanced among the Oleandraceae, and that Cymnogram- miiis represents the more primitive element in the Davalliaceae.

I ntroduction communication attempts to describe the spores of the Davalliaceae and Oleandra­ In a series of earlier communications ceae (together included in the Davalliaceae we described the spore morphology of the by Copeland, 1947), and includes nine major groups of ferns with particular refer­ out of the dozen or so genera included in ence to the Indian species. The present the group. The methods of study as well as of spore description are the same as in 1. Accepted for publication on August 28, earlier communications. The descriptions 1970. 2. Department of Botany. Calicut Univer­ are based on acetoiysed preparations sity, Kerala. mounted in glycerine jelly; notes are added It is a pleasure to record here our grati­ where unacetolysed spores have some tude to Mr. Neil D. Hall of the American Fern characteristic differences from the aceto­ Society, who supplied us several of the spore iysed ones. All measurements recorded samples used in this study. We are thankful also to the authorities of the California Univer­ are the averages based on 10-20 read­ sity Botanical Garden for kindly supplying u& ings in each plane, of spores selected some spore samples. at random. The terminology used is the same as in the earlier papers of this series thicker than nexine, subverrucate-areolate and as described by Nayar (1964). A with verrucae ca. 4 p. across at the complete description is given only of the base, less than 2 |x tall and becoming faint spores of the first specics mentioned under towards the laesura. Ferine absent. each genus; in cases of subsequent Unacet. nearly hyaline and more or less species, only such details in which they of the same size as acet. differ from the first species are mentioned. A. pulchra (Don) Copel. 1805; Natl. Shape of the spore in both lateral and Bot. Gdns. Herbarium; B. K. Nayar polar Views are recorded (the abbreviations 51895. ‘lat’ and ‘pel’ stand for lateral view and Spores 44 (48—4) X 76 |x (range 40 X 68 polar view respectively). To denote to 48 X 88 n) in size. Laesura 26 |ji long, acetolysed and untreated spores the tenuimarginate. Exine 4 |x .thick, light abbreviations ‘acet.’ and ‘unacet.’ are brown. used. The size of the spore is recorded Unacet. 36x 58 [x in size. as polar diameter X longest equatorial Davallia Smith D. canariensis (L.) diameter (for details, see Nayar, 1964). Sm. 1902; Amer. Fern Soc. ex. no. 126 Under each species, reference is made to Spores monolete, bilateral, concavo- the source from which spore sample is convex (lat), elongate-oblong (pol) and 32 obtained for study so as to facilitate cross (36—4) X 52 n (range 28 x 50 to 36 X 56 n) checking if necessary; where samples are in size. Laesura 24 jx long and faintly from herbarium material the name of the crassimarginate. Exine 3 (x thick, light herbarium and the collection number of reddish-brown; sexine much thicker than the specimen are quoted. Several samples nexine, faintly areolate with the areoles were supplied by the American Fern 1 [X tall, 2-3 (X across, irregularly Society’s Spore Exchange Department polygonal, with rounded outer surface and some by the Botanical Garden of the and progressively smaller and fainter California, University, Berkeley. The towards the laesura. Ferine absent. first number quoted in brackets after the Unacet. 28 x 48 jx in size, hyaline to ;iame of each species is the serial number light golden-yellow in colour and with of the spore slide from which observations pale yellowish dense contents. are made; the slides are deposited in the D. chaerophylloides (Foir.) Steud. Sporothek of the National Botanic 1477; Sierra Leone Herbarium, Njala; Gardens, Lucknow. F.C. Deighton 5117. Spores plano-to concavo-convex (lat),

D avalliaceae oblong (pol) and 42x68 jx in size. Laesura faintly incrassate. Exine deep Araiostegla Copel. A. hymenophyl- reddish-brown, subverrucate-areolate with loides (Bl.) Copel. 1897; cult., Univ. the verrucae less than 1 |x tall, 4 |x across, Calif. Bot, Gdns., Berkeley U. S. A. irregularly circular to polygonal in outline Spores monolete, bilateral, concavo- and progressively less prominent towards convex (lat), elongate-oblong (pol) the distal pole. Many aborted spores and 34 X 50 [J. (range 28 X 44 to 40 X 60 fx) occur. in size. Laesure 23 jj. long and incrassate. D. cornlculata Moore 1900; Amer. Exine 3 p, thick, light reddish-brown to Fern Soc. ex. no.l29. Fig. 11, nearly hyaline in colour; sexine much Spores ovate (pol) and 30 X 52 |x (range 24 x 48 to 3 2 x 5 6 (x) in size. Laesura subverrucate-areolate with the verrucae tenuimarginate and sometimes forked at 4-6 (X broad. the tip. Exine 4 thick (nexine with a Unacet. nearly hyaline in colour and yellowish tinge), subverrucate-areolate containing a few large, nearly colourless with the verrucae 3-6 (x across and 1 (x plastids. tall. D. fijienslt Diels 1661; Amer. Fern Unacet. nearly of the same size as acet., Soc. ex. no. 89 . light yellowish with a greenish tinge, Spores piano- to slightly concavo-convex containing a few small light-green plastids (lat), oblong (pol) and 42 x 56 (x (range and with the exine appearing nearly 36 X 52 to 44 X 64 jx) in size. Laesura 22 |x smooth, long and incrassate. Exine subverrucate- D. denticulata (Biirm.) Mett. 1664; areolate with the verrucae prominent, Sarawak Museum, Kuching; W.M.A. nearly circular, uniform, deeper in colour Brooke 8052. than the exine, ca. 8 [x across and 2 (i Spores piano- to slightly concavo-convex tall. (lat), oblong (pol) and 32x52 [j. (range Unacet. ra. 34x50 jx in size, hyaline 2 7 x43 to 3 2 x 5 4 [j.) in size. Laesura in colour and containing one to three 22 (X long and faintly incrassate. Exine colourless oil globules and many small subverrucate-areolate with the verrucae plastids. ca. 2 [X tall, 4 |x broad and rather faint D. marieti! Moore 1903; Amer. Fern around the laesura. Soc. ex. no. 352. Unacet. 2 6 x 4 2 (x in size, hyaline in Spores piano- to slightly concavo-convex colour and containing one or two nearly (lat), ovate (pol) and 36 (40-4) x 58 [x hyaline oil globules and a few small (range 3 6 x 5 6 to 4 0 x 6 0 (x) in sizei plastids. Laesura 22 [x long and tenuimarginate. D. divaricata Bl. 1647; Amer. Fern Exine 3‘5 (x thick, dull brown with a Soc. ex. no. 269. Fig. 4. blackish tinge, and areolate with the Spores piano- to slightly concavo-convex areolae often polygonal in surface view, (lat), ovate to elliptic (pol) and 37x60 [x with nearly straight sides, usually 4 jx (range 3 2 x 4 8 to 4 4 x 6 8 jx) in size. across, 3 jx tall, more prominent towards Laesura 30 [x long and tenuimarginate. the distal side and very faint around the Exine nearly hyaline to very pale brownish laesura. , and densely verrucate, with the verrucae Unacet. nearly of the same size as acet., 6 (X across, 2-3 (x tall, subhemispherical hyaline in colour and with dense yellow, and uniform all over. contents. Unacet. 24x42 (x in size, nearly hyaline D. multidentata (W all) Hooker 1867; in colour and with dense yellowish contents cult., Natl. Bot, Gdns., Lucknow. including a few small plastids. Spores piano- to slightly concavo- con­ D. d itsecta J. Sm. 1669; Bogor vex (lat), elongate-oblong to ovate (pol) Herbarium, Indonesia; J. A. Lorzing and 32x48 (x (range 24x44 to 40x52(x) 8953. in size. Laesura 18 (x long and faintly Spores piano- to slightly concavo- crassimarginate, Exine 2'5 (x thick, deep convex (lat) oblong (pol) and 44 x 62 (x brown with a darkish tinge and subverru­ (range 3 6 x 4 0 to 4 8 x 6 8 (x) in size. cate-areolate with the verrucae ca. 4 Laesura 22 [i long and incrassate. Exine across at the base. Unacet. ca. 26 x 40 t* in size with the verrucate-areolate with the verrucae less exine hyaline in colour and contents than 1 tall and ca. 4 [x across. yellow throughout and includiug a few Unacet. 20 X 38 [x in size, nearly hya­ large light green plastids. line and with dense yellowish contents. D. pyxidata Cav. 1507; School of Biol. D. v'iscldulum (Mett.) v. A. v. R. 1654; Sci., Univ. Sydney, Australia, ex. no. Bogor Herbarium, Indonesia; Posthumus 165j. Fig. 5. 3561. Spores plano-convex (lat), oblong (pel) Spores piano- to slightly concavo-con­ and 26x45 (J. (range 24x32 to 32x52 \j.) vex (lat) and 35x56(1 (range 32 X 52 to in size. Laesura 26 long and faintly 36 X 60 ix) in size. Laesura 22 (x long and incrassate. Exine 2’5 n thick, light yellow­ tenuimarginate. Exine 3 (x thick; sexine ish-brown, densely tuberculate with the slightly thicker than nexine and with the tubercles ca. 8 t* across, 4 y. tall irre­ areolae 1 (x tall, less then 4 (x across and gular in outline. uniform throughout. D, Mollda (Forst.) Sw. 1802; Sarawak Gymnogrammltls Ching G. dariefor- Museum, Kuching; Clemens, 2145. Fig. (Hook.) Ching 1925; Natl. Bot Gdns. 12. Herbarium, Lucknow; Anonymous 6566. Spores piano- to slightly concavo-convex Spores monolete, bilateral, concavo- (lat), oblong (pol) and 38 (41—3) X 60 convex to piano convex (lat), elongate- (range 30x 48 to 44 X 62 :a) in size. Lae­ oblong (pol) and 44 X 76 [X (range 38 x 68 sura 24 (i. long and faintly incrassate. to 52x 80 (x) in size. Laesura 26 [x long Exine very pale yellowish-brown and and crassimarginate. Exine less than 2 (x subverrucate-areolate with the verrucae thick, pale brownish to nearly hyaline in ca. 2 (A tail and 6 across. colour; sexine nearly as thick as nexine Unacet. 28 (30—2) x 40 in size and and densely but faintly granulose. Ferine hyaline to very pale yellow in colour. absent, Devallodes CopeJ. D. borneense Unacet. nearly hyaline in colour and (Hooker) Copel. 1905; cult.,Bot. Gdn., 40 x 70 [X in size. Singapore. Humata Cav. H. tyermanni Moore Spores monolete, bilateral, planoconvex 1769; cult., Exptl. Gdns., Univ. Bruxelles, (lat), oblong (pol) and 36x44 (range Belgium. Fig. 2. 28 X 36 to 44 X 52 (i) in size. Laesura Spores monolete, bilateral, concavo- 15 n long, faintly crassimarginate and convex to plano-convex (lat), oblong ovate sometimes forked at the tip. Exine 4 (x (pol) and 34 (37 —3) x 52 (x (range 3 2 x 4 8 thick, light blown; sexine much thicker to 4 4 x 6 4 n) in size. Laesura 18 fx long than nexine, faintly areolate with the and tenuimarginate. Exine golden brown, areolae irregular in outline, having nearly 3 ix thick; sexine nearly as thick as nexine, flat surface, ca. 4 (j. across, 1 (ji tall and densely subverrucate-areolate with the uniform all over. Ferine absent. verrucae less than 2 (x tali and 4-6 (x D. hirsutom (J. Sm.) Copel. 1650; cult., across on the distal surface (but progres­ Bot. Gdn., Bogor. sively smaller towards the proximal pole) Spores piano- to slightly concavo-con­ and irregular in outline. Ferine absent. vex (lat) and 36x^8 n (range 32x44 to Leucostegia Fresl L. im m ersa (Wall.) 36x52 1*) in size. Laesura 18 (x long, Fresl (715; Nat. Bot. Gdns. Herbarium, tenuimftfginate. Exine 3 thick and sub­ Lucknow; B. K. Nayar 63483. Figs. 3, 13, Spores monolete, bilateral, concavo- 24 X 32 to 28 x 40 (i) in size. Laesura 16{i convex (lat), elongate-oblong to ovate long. Exine 1'5 (x thick. Ferine closely (pol) and 30 X 50 (A (range 20 X 44 to 38 X adherent to exine and wrinkled into short 56 [i) in size. Laesura 23 fx long and in- irregular flap-like folds protruding 4-8 (i crassate. Exine 3 ia thick, palp yellow in from the exine surface. colour; sexine almost as thick as nexine, Unacet. nearly of the same size and densely tuberculate with the tubercles colour as the acet. and containing a few rather irregular in shape, with rounded globose plastids and yellowish oil globules. outer surface, 6-8 tall, 10-20 [x across A. tenella (Forst,) J. Sm. 1778; Amer. nearly uniform (except around the laesura Fern Soc. ex. no. 14. Fig. 14. where they are slightly smaller) and Spores oblong (pol) and 30x42 (x in having a granulose surface. size. Laesura 26 tx long. Exine yellow in colour, thin and smooth. Ferine OLF.ANDRACF.AE prominently granulose and sparsely spin- ose, rather adherent to the exine and Aritbropteris J. Sm. A. becklerii faintly wrinkled or with a few sharp folds (Hooker) Mett. 1809; Bola Creek National protruding ca. 4- 8 [x from exine surface; Par k, N. S. W., Australia; M. Tindale spines 4-6 [x long, deciduous, sometimes s. n. Fig. 15. very few. Spores monolete, bilateral, plano-con­ Unacet. nearly of the same colour and vex (lat), ovate (pol) and 35x52 [x (range size as the acet. 2 8 x48 to 4 0 x 6 0 [j.) in size. Laesura Nephrolepis Schott N. biserrata 30 long and tenuimarginate. Exine 3 (Sw.) Schott 1330; Forest Herbarium, thick, light brown; sexine almost as thick Ibaden, Nigeria; D. F. Stanfield 45534. as nexine and smooth. Ferine light brown Fig. 17. granulose with the granules prominent Spores monolete, bilateral, plano-convex (some rugula-like) and forming a reticulate to slightly concavo-convex (lat), ovate pattern having fine meshes, and sparsely (pol) and 22 X 32 (j. in size. Laesura 17 (x wrinkled into flap-like, thin, sharp folds long and tenuimarginate. Exine 2 5 |x ca. 12 high, papillate in optical section, thick, dull brown, not clearly subdivided appearing like spines and with irregularly into sexine and nexine and smooth. angular crest. Ferine very closely adherent to exine and A. monocarpa (Cordem) C. Chr 1470; not clearly distinct from it, smooth and Sierra Leone Herbarium, Njala; T.S. Jones wrinkled into tubercle-like crowded folds 340. Fig. 10. which are irregular in outline, ca. 2 5 Spores oblong (pol) and 32 x 43 [x in tall, 4 across, sometimes slightly elon­ size. Exine 2 5 thick. Ferine faintly gated (some of the smaller ones rugula- granulose and with its folds prominent, like) and nearly absent on the proximal elongated, slightly sinuous, flap-like, up to surface above the laesural region. 13 [i tall, sometimes forming an irregular Unacet. nearly of the same size as acet., lophate pattern and with irregularly wavy light brown in colour and containing a to nearly smooth crest. few small plastids and dense cytoplasmic A. orientalis (Gmel.) C. Chr. 1904; contents. Amer. Fern Soc. ex. no. 324. Fig. 9. N. cordifoUa (L.) Pr, 1666; Amer. Spores oblong (pol) and 26 x 36 jx (range Fern Soc. ex. no.2 10. ' Spores oblong (poJ) and 2 0 x 3 4 n Spores nlonolete, bilateral, 28 x 35 (Jt (range 15 x 28 to 24 X 36 fi) in size. Laesura (range 24 x 32 to 32 x 40 in size, 12 /i long, Exine brown; sexine almost plano-convex to slightly concavo-convex as thick as nexine. Ferine wrinkled into (lat) and elliptic-oblong (pol). Laesura large rugula-like folds which are crowded 15n long and tenuimarginate. Exine (often coalesced to form irregular reticula­ 2-5fi. thick, deep brown ; sexine almost as tions), commonly ca. 4 ^ broad, less than thick as nexine, densely spinulose with the 2 iJ- tall and progressively less conspicuous spinules acicular, straight, up to 3 n tall towards the proximal pole (with nearly no ca. V5 [i across at the base and tapered folds opposite to the laesura). to a sharp apex. Ferine hyaline to light linacet. nearly of the same size and brown in colour, rather adherent to the colour as the acet. exine, sparsely spinulose (spinules nearly N. exaltata (L.) Schott 1909: cult., hyaline to light brown in colour), and Nat. Bot. Gdns., Lucknow. Fig. 18. wrinkled into elongated thin, sinuous Spores concavo-convex (lat), oblong folds (which rarely form an incomplete (pol) and 18 (20-2) x 30 in size. Laesura lophate pattern) having irregularly angu­ 12 n long and faintly incrassate, Exine lar crest and protruding up to 6 n from 3 thick, light reddish-brown; sexine the exine surface. nearly as thick as nexine. Ferine closely Unacet. nearly of the same size and adherent to and nearly indistinguishable colour as the acet. and with contents from exine and with the folds tubercle­ masked by the spore-coat. like; tubercles irregular in shape and more O. m usifolia (Bl.) Pr. 1545 ; Nat. Bot. prominent on the distal face than on the Gdns. Herbarium, Lucknow ; F. Chandra proximal. & S. Chandra, s. n. Unacet. slightly darker in colour and Spores 24x37 (range 18x22 to nearly of the same size as acet. 2 8 x 4 0 [x) in size. Exine dark brow n; N. undulata (Afzel, ex Sw.) J. Sm. spinules ca. 3 |j. tall, less than 1 across 1344; Forest Herbarium, Ibaden, Nigeria; at the base and with a sharp apex. Ferine D. P. Stanfield 45533. Fig 1,16. brown, rather loose and sparsely spinose Spores plano-convex (lat) and 26 X41 (spines up to 5 |j. tall, slender and with a in size. Laesura 28 long. Exine 1’5 |j, sharp apex); folds of perine narrowly thick, darkish-brown; sexine almost as conical in optical section, often coalesced thick as nexine and densely and uniformly to form an irregular lophate pattern, spinulose with the spinuless lender, sharp, and protruding up to 12 ^ from the exine less than 2 ^ tall and dark brown. surface. Ferine loose, spinulose (spinules ca. 2 O. pistillaris Pr. 515 ; Nat. Bot. Gdns. long, pale brown, slender, sharp), light Herbarium, Lucknow; B .K. Nayar brown in colour and wrinkled into more 77311. Fig. 8, 21. or less sparse lobate folds with irregularly Spores 25x34 (range 23x32 to angular crests, broadly conical in optical 2 8 x 4 4 n) in size and oblong (pol). section, and protruding ca. 8-10 from Exine light brown ; sexine much the exine surface. thicker than nexine and with the Oleandra Cav. O. dlstenta Kze. 1484; spinules thin, sharp, ca. 4 ii tall and 1-5 Sierra Leone Herbarium, Njala ; W. across at the base. Perine loose, light Jackson 27. Fig. 6, 19. brown, minutely spinulose (spinules dense,

4 |i tall, sharp), and with its folds scarcely ing to Holttum (1947), Orthiopteris ac­ sinuous, broadly conical in optical sec­ cording to Copeland (1947) and C ukita tion, having crenate crests and protruding according to Ching (1940). The davalli- up to 8 iJ. from the exine surface. oid genera are regarded as comparatively O. wallichU (Hook) Pr. 515; Nat. more advanced, with Oleandra related to Bot. Gdns. Herbarium, Lucknow ; B. K. them through genera like Humata accord­ Nayar 77355. Figs. 7, 20. ing to Copeland ; Holttum believes that Spores 26x37 |J. (range 24x32 to 28 the davallioid ferns are independently x40 (J.) in size. Laesura 12 long. Ex­ derived from Microlepia whereas Oleandra ine smooth. Ferine densely spinulose is derived from Nephrolepis. According (spinules up to 8 |J. tall, sharp or blunt, 2|x to Ching both the davallioid ferns and across at the base but often rather flat­ Oleandra are derived from Nephrolepis. tened and some of the adjacent ones coal­ Spore morphology of nearly a dozen esced to form ridges at the base), closely species of the Davallia-Oleandra group adhering to the exine and wrinkled into of ferns is described by various authors broad, blunt, irregular, reticulated folds (Harris, 1955; Erdtman, 1957; Tardieu- which are narrowly conical in optical sec­ Blot, 1964); the data is reviewed recently tion and with irregular crest. by Braggio (1966) along with datailed description of another 20 species. Thus, D is c u s s io n spores of all genera of the group except Trogostolon, Scyphularia and Parawrus The Davallia-Oleandra group of genera are known in some detail. The present are regarded by taxonomists as a closely observations differ from those of pre­ allied group, close enough according to vious authors in the following details some (Copeland, 1947) to be included (/) Spores of Nephrolepis are described as under a single family (Davalliaceae). deviod of perine (Harris, 1955; Tardieu- Though as a group these ferns are regard­ Blot, 1964; Braggio, 1966), the protuber­ ed as of ambiguous affinity, most pterido- ances on the surface of the spore logists regard them as derived from the being interpreted as exine excrescences. dicksonioid dennstaedtioid stock. An en­ Though in N. undulata a loose, spinulose tirely different hypothesis of relationships perine is evident, it is not clearly is presented recently by Nayar (1970). demarcated in many species, but its According to him the Oleandraceae and presence as a layer closely adherent to the Davalliaceae, represent two distinct but exine is easily distinguished. Also, occa­ parallel lines of evolution, related to the sionally the perine cracks and peels off dryopteridoid complex (both having a from the spore and when thus peeled it remote common ancestry) and thus be­ is clearly seen that the ‘protuberances’ are longing to the cyatheoid line of descent. merely folds, (ii) A closely adherent The dicksonioid-dennsteadtioid series is perine is reported in Davallia cheiro- regarded by him as not closely allied to phylloides by Tardieu-Blot (1964). None the Oleandra-Davallia group. Arthrop- of the species, including D. cheirophylloi- leris and Nephrolepis are regarded by most des, in our study show any trace of a pteridologists as the more primitive ele­ perine. Our observations are in confor­ ments in the group. These genera are mity with those of Braggio (1966). {Hi) derived directly from Microlepia accord­ A perine is reported in Humata repens by Tardieu-Blot (1964). The spores of H. (Tardieu-Blot, 1964). tyermanni studied by us are distinctly rton- Among the Davalliaceae there is some perinate as are the spores of //. kinabal- range of variation in spore size and in the vensis (Braggio, 1966). (n) Braggio nature of the ornamentation on the exine. (1966) reports a distinct, loose, saccate, In size the acetolysed spores vary from scarcely folded perine in Araiostegia pul- ca. 3 0x 52 [j. in D. canariensis, D. corni- chra and A. hymenophylhndes. Our culata, D. denticulata, D. multidcntata, material of both these species lacks any D. pyxidala and Leucostegia immersa, to trace of perine. (v) The spores of Nephro- 44x78 [J. in Araiostegia pulchra and Icpis exaltafa studied by Braggio (1966) Gymnogrammitis dareiformis and 42 x 68 from Cuba are markedly larger than (j. in D. clieirophylloides. Acetolysis those of the Indian material studied by us. markedly increases the spore' size in the On the basis of spore morphology the family, the polar diameter increasing by Davalliaceae are clearly distinct from the 27-75% and the equatorial diameter by Oleandraceae, the former possessing spore 12-45%. Unacetoiysed spores range devoid of perine and having heavy-set from 20x38 ix (Davallodes hirsutum) to areolate or tuberculate type of exine orna­ 35-40x60-65 [j. (A. pulchra, G. darei­ mentation, and the latter possessing peri- formis). The exine ornamentation varies nate spores with exine either smooth or from granulose as in G. dareiformis to bearing delicate spinulose or spinose orna­ tuberculate as in Davallia pyxidala and mentation. Also, the spores are charac­ Leucostegia immersa, the majority having teristically larger (ca. 35x50[j. on an a subverrucate-areolate ornamentation. average) in the Davalliaceae than in the It seems probable that those species with Oleandraceae (ca. 26 x 37 [^) and they more prominent sculpturing on the exine swell markedly on acetolysis in the fomer are comparatively more advanced, since a whereas there is little alteration in size smooth spore coat among homosporous on acetolysis in the latter. This supports ferns commonly denotes a primitive the separation of the two families as nature. Thus, Leucostegia immersa with advocated by most of the contemporary its prominently tuberculate exine appears taxonomists. In merging the Olean­ to be comparatively an advanced taxon draceae with the Davalliaceae, Copeland in the family rather than a primitive one (1947) was guided by the supposed as suggested by Copeland (1947). Also, relationship between Oleandra and Humata and Davallodes appear to be Humata. As pointed out above, the comparatively primitive genera. By far spores of these genera are characteristic­ the least specialised taxon in the group ally different, indicating that these genera is Gymnogrammitis, which possesses the are not so closely related, Humata having largest spore with granulose exine. non-perinate spores distinctly of the Among the Oleandraceae spore morpho­ Davallia-type. Rumohra (sensu stricto) is logy appears to support the contention commonly regarded as a davallioid genus. that Nephrolepis is comparatively the However, the spores of both the species primitive genus as suggested by Copeland of the genus are more like those of (1947). The majority of species possess the Oleandraceae than the Davalliaceae an ill-differentiated perine which is skin­ in their smaller size (24x35 [j.) and in like and wrinkled into small blunt irregu­ having a smooth exine and distinct perine lar faint tubercle-like folds, and both the exine and perine are smooth. However, that these genera are not closely allied to in some species like N. mdulata the them. On the basis of the spores perine is well diiferentiated, and both the Arthropteris is associated by him with exine as well as the perine are spinulose Arachniodes and Didymochlaena, both recalling Oleandra. In possessing a loose dryopteridaceous genera. There may be granulose perine apparently is some relationship between these genera, more advanced than the majority of species possibly in having a common ancestry as of Nephrolepis. Also, A. tenella possesses suggested by Nayar (1970), but the spores spinulose ornamentation on the perine of Arthropteris are essentially similar to recalling Oleandra and Nephrolepis those of Nephrolepis and Rumohra, mdulata. Oleandra is apparently the justifying its inclusion in the Oleandraceae. most advanced genus in the group, with As mentioned above, the dicksonioid- its characteristic spinulose to spinose dennstaedtioid group of ferns are regarded ornamentation of the exine as well as by most pteridologists as the source from perine. This supports the conclusion which the Davallia-0/£Wi(//'a group based on sporophytic and prothallial evolved; Microlepia, Orlhiopteris and morphology (Nayar and Devi 1968). In Culcita are mentioned in literature as the a dozen or so species of which spore probable ancestral types. In all these morphology is known (Braggio, 1966) the ferns the spores are of the trilete- exine is spinulose to spinose except in tetrahedral type (Nayar and Devi, 1968) O. wallichii, the perine is spinulose in all devoid of any perine. In Microlepia the except probably O. costaricensis (Braggio, exine is smooth to granulose, in 1966). Apparently, such species as O. Orthiopteris smooth and in Culcita ejurana, O. distenta and O. musifolia areolate (Devi, 1966). In the nature of having prominently ornamented exine as the exine ornamentation the Davalliaceae well as perine are comparatively more resemble Culcita most. Among homo- advanced in the genus. sporous ferns monolete perinate spores are On the basis of spore morphology nearly restricted to the genera of the Braggio (1966 ;) concluded that Olean­ dryopteridoid complex, viz. Dryopterida- dra “represents an independent paly- ceae, Lomariopsidaceae, Thelypteridaceae, nological entity...... justifying treating Aspleniaceae and Blechnaceae, all of Oleandra as the only member of an which according to Nayar (1970) are of independent family Oleandraceae”. The cyatheaceous aflSnity. Oleandraceae presence of spores similar to that of shares this character, and in addition are Oleandra in Nephrolepis mdulata contra­ reported to have several characters in dicts this view, clearly indicating that common in prothallial morphology (Nayar Oleandra should properly belong to the et al., 1967; W agner, 1952). Also, as Nephrolepis group as suggested by Nayar in Nephrolepis, an incipient perine is (1970). According to Braggio (1966) found in some genera of the Dryopterid- spore morphology indicates that Ncphro- aceae, Thelypteridaceae and Blechnaceae lepis and Rumohra are closely allied to the (Nayar and Devi, 1963, 1964a, b; Nayar Davalliaceae. That both these genera and Chandra, 1966; N ayar et al., 1964, possess perinate spores and differ from 1966). However, the type of exine the Davalliaceae in their markedly smaller ornamentation as found in the Davalli­ spores appear on the contrary to indicate aceae is uncommon among the ferns of the Dryopteridaceae complex, though (Devi, 1966); it strongly recalls tlie spores spores with tuberculate ornamentation of of the Polypodiaceae (Nayar and Devi, exine are reported in some species of 1964c). Cyathea, like C. mexicana and C. vestita

R eferences

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