72 



OPHIOGLOSSACEAE 

 A ..—r-^ B 



[CH. 



Fig. 371. Botrychium daucifoliiim Wall. A and C, successive stages of the most 

 common type of sporangium; B, a small narrow form; D, a very broad 

 sporangium : the cells marked ( x ) correspond to the sporogenous group, but 

 show no signs of developing further as such ; E, a still broader sporangium with 

 wide sporogenous group, referable to two parent cells, possibly ultimately to 

 one; F, G, synangia cut transversely and vertically. ( x 200.) 



transitions between the separate sporangia of BotrycJiiiivi and the S3mangial 

 state of Opliioglossinn. Whether the facts will bear any evolutionary inter- 

 pretation, as illustrating the manner of advance from a simpler or a reduction 

 from a more complex state, may be a question for discussion. But it is clear 

 that transitional forms exist. 



The origin of the spike of HelinintJiostachys and its early structure 

 resemble that of the other genera: but its tip is curved over while young, 

 and is protected by the segments of the sterile frond, which are themselves in- 

 vested at first by the stipular sheath of the next older leaf. The young spike 

 seen from without appears as in Fig. 372. The young sporangiophores, very 

 variable in size and arrangement, are densely clustered along the margins, 

 corresponding thus roughly in position to the marginal rows of sporangia 

 in the other genera. Transverse sections through the lateral regions corre- 

 sponding to the sporangiogenic band of OpJiioglossuui disclose a fan-like 

 tracery of the cell-walls with rather deep superficial cells (Fig. 373, a). It is 

 from these that the sporangiophores originate, as outgrowths very irregular 

 in size and arrangement (Figs. 373 c, 374 a). There seems to be no fixed 

 type of segmentation of the cells which form them. As they increase in size 

 their apex may be occupied by a wedge-shaped cell; more frequently no 



