270 



BOTAKY 



Order II. Marattiaceae 



The Marattiaceae include a small number of tropical forms which 

 resemble, in their general appearance, the typical Ferns. The sporo- 

 phyte may be of large size, as in Angiopteris and some species of 

 Marattia, where the thick, tuber-like stem is half a metre or more in 

 diameter, with a crown of thick leaves three to four metres or more 

 in length. 



FIG. 236. Marattia Douglasii. Embryo. A, longitudinal, B, transverse, sections 

 of embryo ( X 215) . C, vertical section of older embryo, showing its position in 

 the prothallium (X 72) ; ur, archegonium. D, upper part of same embryo (X 215). 



The Gametophyte 



The small, colorless spores germinate slowly, the first division occurring in 

 about a month after the spores are sown. The gametophyte (Fig. 205) is a fleshy 

 green thallus, much like a Liverwort in appearance, and upon it are borne both 

 antheridia and archegonia. The latter are confined to the lower side, as they 

 are in the common Ferns. In structure, the sexual organs (Fig. 235) closely 

 resemble those of the Ophioglossacese, but the outer wall of the antheridium 

 has but a single layer of cells, and opens by a small triangular opercular cell. 

 The archegonium neck is very short. 



The gametophyte frequently multiplies by the formation of adventitious buds, 

 and the apex may fork exactly as in a thallose Liverwort. 



Embryo. As in Botrychium, the basal wall of the embryo is transverse, and 

 the differentiation of the organs is slow, so that the embryo remains long de- 



