m] 



CHAMBERLAIN— SPERMATOGENESIS IN DIOON 



217 



The number of sporangia on the larger sporophylls varies from 



about 100 to 300; but the smaller sporophylls bear fewer, and the 



porophylls at the apex and base of the cone may bear only a few 



porangia, or even none at all. 



The sporangia are grouped in definite sori, usually of four 

 or five sporangia, as shown in fig. 2. At the stage shown in this figure 

 the line of dehiscence is quite 

 obvious. As the sporangia dehisce, 

 the grouping into sori becomes 

 less obvious. The pollen does not 

 escape immediately, but for a short 

 time is held together in a spherical 

 mass by the scantv remains of the 

 hypodermal wall 



layers. A hand 



sorus is sur- 



lens shows that each 

 rounded by hairs which grow out 

 rom the peripheral portion of the 



*•'*' 



base of the sorus. 



Many 



grow out from the peripheral por- 

 tions of the sporangia, but there 

 "e none in the interior of the sorus, 

 «ther upon the sporangia or upon 

 the sporophyll (fig. 4 ) . 



rp, ° ^' J?IG. 2. — rnOTOgrapua v» — - ■ 



^e s porangia are either sessile sp oro P hylls of Dioon edule. xj. 

 or have short massive stalks. The 



Wfa and even the lower portions of th : " " f - -"" ™ 



somewhat united, but there is not so 



Fig. 2.— Photographs of two micro- 



m 



deh 



Miss Smith (8) 



much 

 The 



hiscence, i n surface view and in section, is about as figured by 

 -a* Swm (g) for Zamia and Enceohalartos. 



Th 



e general appearance of a sporophyll in transverse section 



> 



\v 



k 



ith 

 A 



*hich 

 hairs. 



fig 



J 



sorus 



The 



specially those which 



come from 



are often so 



and 



a 



I ar enchy ma tissue of angular cells than like sections of tubular hairs 



