XX] HABIT 97 



which are connected across the adaxial face of the petiole by a transverse 

 commissure (Fig. 390; see also Vol. I, Fig. 96). Though these are charac- 

 teristic for all the adult Marattiaceae, they are absent from the first and often 

 from the second leaf of the sporeling. After the upper leaf decays they 

 remain persistent, in close relation to the smooth scar which marks its 

 attachment. 



Scott {Attn, of Bot. Vol. xxvi, 1912, p. 60) has discussed the aphlebiae seen in Zygopteris 

 . Grayi, regarding them as modified pinnae of the leaf which have spread downwards on to 

 the stem, but they were always in definite relation by their vascular strands with the leaf- 

 traces. Their function was the protection of the growing points and young leaves. Basal 

 growths laterally on the petioles are widely spread among living Ferns of primitive type, 

 such as the Marattiaceae. It may be a question whether these are truly homologous with 

 the basal aphlebiae of the Coenopterids ; but in any case they correspond in position and 

 in function. Such modern basal growths as those of the Ophioglossaceae, Marattiaceae, 

 and Osmundaceae have been described as stipules, and they appear highly variable both in 

 bulk and in the presence of a commissure, and may provisionally be held as being parts of 

 the same nature as the basal aphlebiae. Buds, often described as adventitious, are formed 

 on the stipules of the Marattiaceae, and propagate the plants if the stipules bearing them 

 are cut away. These buds are stated not to be really adventitious, but to be laid down 

 early, remaining dormant as are the axillary buds in Helmiiithostachys (Van Leewin, Bait. 

 A?m. Vol. X, p. 202). 



The upper leaf of the living genera varies considerably. It may be simply 

 ovate, with marked midrib and acuminate apex, as in Macroglossum or 

 Danaea simplicifolia: or it may be simply pinnate, as in D. alata (Fig. 389), 

 or in ArcJiangiopteris and Protomarattia: or the pinnation may be repeated, 

 as in Marattia or Angiopteris (Fig. 388). In large plants the leaf may 

 attain a high complexity of branching, while its length may be as much as 

 15 feet. In Christensenia the outline of the leaf differs from all the rest: the 

 long petiole bears five palmately disposed lobes of broadly lanceolate form, 

 with a general similarity of outline to the leaf of the Horse Chestnut 

 (Fig, 392, D). The venation is simple and dichotomous in all the other genera, 

 with open endings to the veins; but it is reticulate in Christensenia, 

 approaching that of the Drynaria-ty^e. The base of the leaf-stalk, and often 

 the bases of the pinnae also, bear fleshy swellings or pulvini: here the stalk 

 is liable to break on decay, leaving a clean scar. The texture of the leaf is 

 usually leathery, but in Danaea trichonianoides there is a thin almost filmy 

 character of the foliage, in obvious adaptation to its moist habitat. 



The young surfaces of Marattia and Angiopteris are covered with hairs 

 which are short and simple, while their terminal cells contain tannin and 

 stain deeply. But in Christensenia and especially in Danaea conspicuous 

 scales of a peculiar peltate form are abundant (Campbell, Eusp. Ferns, p. 1 50). 

 Elongated scales of considerable size are present on the leaf-stalks of Proto- 

 marattia (Hayata, Bot. Gaz. Ixvii, PI. I, Fig. 4. 1919). A like condition 



B. II. 7 



