SPORE-PRODUCING MEMBERS 315 
assist in conveyance of nourishment to the large mass of developing 
spores. Thus in the main features of form and dehiscence the sporangia 
of Rhopalostachya conform to the type of Z. Se/ago, but are larger and 
more productive; while the sporophylls have a more elaborate form for 
purposes of protection. This goes along with the differentiation of the 
vegetative from the propagative regions, the steps of which have been 
traced above in the genus Lycopodium. The conclusion seems justly to 
follow that with this differentiation, which has apparently involved a 
diminution in the actual number of sporangia by abortion, there has come 
A B 
Fic. 161. 
Lycopodium alpinum, L. A=Radial section through a sporophyll and young 
sporangium. =the same older; in both the sporogenous tissue is shaded. D=radial 
section of an older sporangium ; s¢=stem. C=tangential section of a sporangium of Lyc. 
clavatum, of similar age to D; in both these figures the sporogenous'’tissue is referable 
in origin to three rows of cells. A,B, CxX200. DX 100. 
into existence a more massive type of sporangium, together with a more 
extensive spore-output from each of them, and a more specialised protec- 
tion of them while young. 
It has been seen that the strobilus of Phyoglossum resembles that of 
the sub-genus Urostachya, rather than that of Ahopalostachya. An exami- 
nation of the developing sporangium supports this comparison, for only a 
single row of about six archesporial cells is found; but, on the other 
hand, the outline of the sporangium, and the relative thickness of the 
stalk, show some similarity to Z. zmundatum. , 
The sporangium of Se/agine//a corresponds in general type to that of 
Lycopodium. It is usually described as arising from the surface of the 
axis: in some species it does so (S, Martensiz) (Fig. 162), but in others 
it is seated more nearly upon the surface of the leaf; in fact its position 
