[64 



SCHIZAEACEAE 



[CH. 



The sporangia alternate right and left of the midrib. The development 

 shows that the origin of the sporangium is from a four-angled cell of the 

 marginal series (Fig. 447, A). Almost immediately after the identity of the 

 sporangium is established by segmentation the growth of the indusium 

 begins (Fig. 447, B, C, i). This is at first semi-circular, and the two sides of 



Fig. 447. Origin of the marginal "monangial" sorus of Lygodutni. ^=margin of young 

 pinnule in surface view: w = marginal cells: j/!i=: sporangium. 8 — 2. similar pinnule in 

 surface view: «/ = apex: 2 = indusium. {A, B, after Prantl.) C=a similar pinnule in 

 section. (After Binford.) 



it differentiate as it develops; the upper more robust lip takes the character 

 of the blade with which it appears to be continuous: the lower remains 

 membranous. The consequence is that the originally marginal sporangium 

 appears as though attached to the lower surface of the adult segment (Fig. 

 441, C). 



A similar slide from a marginal to a superficial position appears in Schizaea. 

 The fertile leaf is circinate, but with the pinnae reflexed (Fig. 448, A, B). If 



Fig. 448. Schizaea rupesiris. A, B, young leaves showing circinate vernation, 

 with pinnae reflexed to the convex (abaxial) side. ( x 3.) C, Z>, E, transverse 

 sections of very young pinnae of Schizaea rupestris, showing the marginal 

 origin of the sporangia, which very soon turn inwards towards the lower 

 (abaxial) surface. In D, E, the indusial flaps are appearing right and left. 

 E, G, similar sections of older pinnae with sporangia and indusia more 

 advanced. (x6o.) 



