XX] 



SPORANGIA 



early stage the sporangia begin to project from the soral area as separate 

 outgrowths, but a comparison of the four sporangia shown in Fig. 404, ^, as 

 seen from above, discloses no regular sequence of segmentations. Of those 

 shown, that marked b is the most regular and usual type, and a single 

 superficial cell (here alread}' divided into two) gives rise to the essential part 



A 



Fig. 404. An^opteris evecta Hoffm. ^ = part of a young sorus seen in surface view from without. 

 j5 = verticar (radial) section of a sporangium such as would be seen on cutting a sporangium (b) in 

 Fig. A, along the line indicated. C= vertical section of an older sporangium showing the genetic 

 grouping of cells. Z) = apex of an almost mature sporangium seen from above: such a section as 

 along the line x , x , in Fig. E. ^ = vertical section of a sporangium with spore-mother-cells; the 

 tapetum is marked x. ^= transverse section of an almost mature sporangium: b, ^ = annulus: 

 c = region of dehiscence: a = thin-walled cells which contract. ( x 200.) 



of the sporangium. If a section were taken along a line x, x, through such 

 a sporangium, after it had grown more convex and segmented further, it 

 would appear as in Fig. 404, B, in which the cells shaded correspond to those 

 shaded h\ A. A single cell has divided periclinally: the inner cell gives 

 rise to the sporogenous tissue, and has already divided in A : the outer 



