On the Structure of Hawaiian Tree Ferns, with Notes on the Affinity of the Genus Cibotium* By Yudzuru Ogura With 6 Text Figures When the writer had studied the anatomy of Cibotium Barometz SM. from southern parts of Japan (1927), he desired in vain to study , other species of this genus. Fortunately he had, in the spring of 1930,. an opportunity to visit the Hawaiian Islands and to study the ana- tomical structure of tree ferns, or the Cibolium species, growing there HISTORY AND MATERIAL . The genus Cibotiztm includes a few species growing in tropical regions; three species in the Hawaiian Islands, five in America , and four (sometimes to be included in one species) in Asia . They are mostly tree ferns having tall erect stems, while Asiatic species are small having creeping rhizomes. The anatomical study of Cibotium Barometz has been undertaken. by several authors:-PARMENTIER 1899, GWYNNE-VAUGHAN 1903 , BOWER 1926, OGURA 1927, HAvAT.A. 1929. According to their observa- tions it has a creeping rhizome clothed with long hairs, and in the rhizome is a solenostele or dictyostele without surrounded by the sclerenchymatous sheath, which is one of the characteristics of the Cyatheacean stem. It has no medullary bundle which is also absent throughout the species of Dicksonieae, one of the tribes of the Cyatheaceae. Its petiole contains numerous bundles arranged in a complex manner, characteristic in all species of the Cyatheaceae . On the structure of the stem of other species of this genus there is no detailed study, and it was very desirable to the writer to compare * Contributions to Morphology and Genetic s from the Departments of Plant- Morphology and of Genetics, Botanical Institute, Faculty of Science, Tokyo Imperial University, No.95. [Vol.XLIV, No.525 468 THE BOTANICAL MAGAZINE them with C. Barometz. The petiole of Cibotium, however, has been observed to a certain extent, concerning the arrangement of vascular strands, by THomAE 1886, IIACHMANN1889, PARMENTIER 1899, BERTRAND& CORNAILLE1902, PELOURDE1909. According to them the bundles are arranged in the characteristic manner just as in C. Barometz and Dicksonia. In the Hawaiian Islands are three species known as Cibotium:- C. Chamissoi KAULFUSS, C. Menziesii HOOKER, and C. glaucum HOOKER& ARNOTT. They grow in the rainy parts of all islands, in some cases in dense forests. The writer collected three species of Cibotium at Glenwood on the Island of Hawaii, near the road running from Hilo to the Kilauea Volcano, where a fairly large forest of tree ferns was seen. C. ChaMissoi and C. Menziesii, both very common on the islands, are distinguished easily from each other in the field; the former has a comparatively shorter but thicker trunk than the latter; moreover, hairs are equally golden-yellow in the former, while blackish or brownish on the crown and petiole in the latter. C. glaucum which occurs rarely was not collected in this district, while another species collected seems not to be described in the botanical list. This is recognizable in the field by its slender trunk, small fronds and also by the pale yellow colour of the trunk tissue when cut down. This seems to be a new species, and will be described with Prof. T. NAKAI as Cibotium hawaiense. Cibotiurn(Eucibotium) hawaiense NAKAI & OGURA,sp. nov. Caudexerectus 3-5 metralisaltus potiusgracilis 6-9 cm. diametienscum gemmis adventitiiscrebre ramulosus, juventute pilis cupreo-aureislongissimis saepe 5-6cm. longisdensissime obtectus, inferior rklicibusatro-fuscis fere toto obtectus. Medulla aurescens.Frondes in apicecaudicis congestae alternae 1-2 metralislongae bipinnatae ambitu ovato-oblongae;stipites cum caudiceinarticulati persistentes virides 15-30cm. longi basi 20-25mm.diametientes ubi extus cum pilis aureo-griseiselongatis dense vestiti; rachisfrondis glabra viridis; pinna pinnata infima ambitulanceolata 50-60 cm. longa20-25 cm. lata utroquelatere 25-30 pinnulata, rachi primopilis multicellulatis (cellulisterminalibus elongatis fuscescentibus ceteris brevibus albidis), pilosa demum glabrescente;pinnula subpectinato-pinatifidafere sessilislineari-lanceolata attenuata quam 12mm. brevior 1-2mm. lata chartaceasupra lucida infra glaucescenscum rachibussubfurfuraceo-pilosa, nervis simplicibusvel rarius bifurcatissupra impressis infra elevatis,lobis oblongis utrinque subrevolutis fertilibus praeter apicemutrinque soriferis.Sori marginales secus inargines loborum pinnarum biseriales utrinque 2-5 (1-6). Indusiumfuscescens primo saccatuin maturitate in valvisbirds fere aegualitus (interiore parce minore) apertum 1mm. longum 1-1.5mm. latum subquadrangularibus. Sporangiumlonge stipitatumannulo obliquo incompleto 24-36 cellulato fusco, cellulis stomii 13-15. Paraphyseselongati subfiliformesunicellulati fusci. Sporae tetra- hedralesfuscescentes. Hab. Sept., 1930] OGURA-STRUCTURE OF HAWAIIAN TREE FERNS 469 Hawaii: Hilo insulae Hawaii (Y. OGURA, typus in Herb. limp. Univ. Tokyo). This endemic Cibotium was first recorded by RIPPERTON(1924), a chemist, who investigated the starches of tree ferns in the Hawaiian Islands. He gave the follow- ing sentence (p.3) with a photograph (pl.1, fig.3); " Another species, commonly known as the "Men," is easily recognised in the Hilo district by its very slender trunk, smaller fronds, dull, lusterless, rather scant, yellowish-brown pulu, and nearly naked stipes." In the list of ferns of the Hawaiian Islands published recently by C. CHRISTENSEN (1925), only three well-known species (C. Afenziesii, C. Chamissoi, C. glaucum) were enumerated. The following description is based on' three species mentioned above:-C. Chamissoi, C. Menziesii, and C. hawaiense. STRUCTURE OF THE STEM The stem is erect, usually 3-5m. in height, sometimes reaching more than 10m. in C. Menziesii, and is crowned by some large leaves. The latter remain only at the top of the stem, old ones falling off; they do not fall from their very bases, so that the characteristic scars as seen in some Cyatheacean species are not to be seen on the stern surface, The leaves are arranged on the stem regularly in the intermediate type of 2/5 and 3/8 divergence (cf. RIPPERTON1925,p.6, fig.1). Adven- Fig.1. Cibotium Chamissoi; photograph of a cross section of the stem. Tufty mass outside consists of hairs; root mass has been removed (x 1/2) 470 THE BOTANICAL MAGAZINE [Vol.XLIV, No.525 titious roots are abundantly produced all round the stem covering its surface, and those from the upper parts cover the root mass of the lower parts, thus forming a very thick root cover, which serves to support the large trunk. This tendency is most prominent in C. Chamissoi in which the root mass reaches more than 1m. in diameter, while the stem proper within this mass measures 10cm. in diameter; these features are similar to those of the typical Cyatheaceae. The thickness of the stem is, of course, different in individual plants; in general, C. Ckamissoi is thickest measuring 10-13 cm. in diameter, while C. Menziesii measures 6-11cm., and C. kawaiense 6-9cm. The stems of the three species agree in their essential internal structure. The cross section of the stem is properly circular, but as the parts of attachment of leaf bases bulge out, its outline is rather lobed (Figs. 1-2). In one cross section three to five of such bulged parts are found, each including vascular bundles with various forms of peculiar arrangement, which are going as leaf traces to the petiole. Within the stem is a stelar ring with lobes running nearly parallel to the outline of stein. Its diameter measures about 5cm. in the stem with a diameter of 6cm. The stele is dictyostelic, several leaf gaps overlapping in one cross section. In C. Barometz it is sometimes dictyostelic, sometimes solenostelic. This is, however, not an important difference, fcr, in this case the dictyostely and solenostely are caused merely by the longness or shortness of the internodes. On the periphery of the stem is a thick brown sheath, which is the important protecting tissue, and within the stem such a mechanical tissue no longer exists. The mode of departure of the leaf traces from the stem stele was investigated by means of successive cross sections. It agrees completely with that of C. Barometz. As several leaf gaps overlap, some stages of leaf trace formation may be seen even in one cross section (Figs.1-2). The epidermis and some cell layers underneath are parenchyma- tous, and gradually pass to the thick sheath, whose membrane is very thick, brown in colour. The thickness of this sheath measures 1-2mm., sometimes 3mm. in large stems, and it is very prominent in C. hawaiense reaching more than 4mm. in thickness (Fig.5). Hairs on the stem surface are very long reaching 2-5cm., they are also persistent densely covering the stem surface (Fig.1). They consist always of one cell row. Their wall is thin, yellowish in colour, and as their contents are lost they usually curl up to a certain extent. The stelar ring is 1-1.5mm. in thickness, and consists of an amphiphloic vascular bundle with distinct endodermal layer. The spt., 193o] OGURA—STRUCTURE OF HAWAIIAN TREE FERNS 471 greater part of the stem is occupied by whitishfundamental tissue whose cells contain a great amount of starch grains, which are used by the natives as a source of food. Pig.2. Cibolium Menziesii; cross section of the stem; hairs and root mass have been removed. A, B, position of leaves; sh, sheath; rt, root trace; st. stele; lg, leaf gap; lt, leaf trace: n. netiole base (x 3/4) STRUCTURE OF THE LEAF The leaf is very large, largest in C. Menziesii measuring 2-3'm. or more in length, while in C. Chamissoi 1.5-2m., and in C. hawaiense 1-1.5m. The petiole is fairly long and thick, its basal part covered with long yellowish hairs reaching more than 10cm. in length. They, are always uniseriate like those of the stem. In C. Menziesii, hairsat the distal part of the petiole become hard and brownish or blackish, 472 T HR BOTANICAL MAGAZINE Vo1.