136 



Elementary Biology. 



FIG. 61. Selaginella incEqualifolia. 

 (Sachs.) ' 



and (b) in arrangement. The leaves are all the same size, 

 and are arranged so as to form a four-sided spike, or cone, 



not unlike a fir cone pulled 

 out. As we shall find later 

 on, this simile is a strictly 

 correct one, for the cone 

 of Selaginella is morpho- 

 logically comparable to the 

 cone of a fir, since both 

 bear sporangia or asexual 

 organs of multiplication, 

 although terms which are 

 associated with the true 

 sexual organs have become 

 by long usage attached to 

 the sporangia of the fir 

 cone. 



The sporophyll of Sela- 

 ginella is hollow and spoon- 

 like, broad at its base, and 

 rapidly narrowing to a 

 sharp point. It bears in 

 its axil the sporangium, 

 while between the leaf and 

 the sporangium, and aris- 

 ing from the base of the 

 leaf, is the so-called ligule, 

 a structure which, since it 

 encloses the sporangium 

 and is epidermal in origin, 



A, fertile branch with cone. B. section of -r^t-,^!/-^ \ 11 , in/ln 



cone (enlarged), showing sporangia, con- 1S morphologically an indU- 



J^^5ri^* e1 *^'^ sium - Each sporangium Is 



composed of a short stout 



funicle and a bivalved capsule, composed of one or more 

 layers of chlorophyll-bearing cells. The sporangium appears 

 in Selaginella to originate from the stem, but that fact need 



