ii8 



MARATTIACEAE 



[CH. 



on the separate state of closely ranged sporangia. It is interesting to note 

 that in Danaea and Christensenia the synangial state is accompanied by 

 flattened scales on the rhizome, which may also be held as a feature of 

 advance. A line of evidence bearing on the further longitudinal extension 

 of the synangial sorus is seen in Danaea. Sections superficially through the 

 elongated sorus show great variations in size of the sporangia (Fig. 409). 

 The smaller are frequently grouped in pairs, separated by a thin or even a 

 partial septum. These facts show that the identity of the sporangium is not 

 maintained. When the elongated sorus of Danaea is compared with the 

 compact sorus of Marattia these irregularities suggest that septation may 

 accompany extension. In any case they introduce into the whole problem 

 of the Marattiaceous sorus and its modifications an elasticity of view which 

 may well aid in any final solution. The original type may probably have been 

 a simple, marginal sorus with separate sporangia arranged round a central 

 point, very much as it is seen in so many of the early fossils, and particularly 

 in Etaptcris and Coryncpteris. 



The Gametophyte 



Germination of the spores of the Marattiaceae produces a robust green 

 prothallus, which may perennate. Its form and early segmentation are shown 

 in Fig. 410 for Marattia, and a like form is seen in the other genera. The 



Fig. 410. A, two germinating spores of Marattia fraxiiiea Smith ( x 200) : the remains of the 

 spore-membrane can be seen. B, young gametophyte of same ( x 75). [A, B, after Jonk- 

 man.) C, M. sanihucina Bhtme (X15). D-H, M. Douglasii Bal<er. D-F (xi-^): 

 G, H {x 3) show the young sporophyte. D, E represent tlie same prothallium after an 

 interval of about a year. F is the ventral view of E\ ;-=root, /i' = adventitious bud. 

 (After Campbell.) 



