CHAPTER ALY. 
THE SPORE-PRODUCING MEMBERS. 
So far only the vegetative organs have been considered in this summary 
of results ; the reason for this is that they appear the first in the individual 
life of Vascular Plants, and it is only after the vegetative system of the 
sporophyte has been established that spore-production supervenes. The 
relation of the sterile to the fertile region from the point of view of 
descent has, however, been discussed at length in Chapter XIII.: the 
conclusion was there reached that in vascular plants the sterile 
tract, which is prior in the individual life, is itself from the evolutionary 
point of view, the consequence of a secondary change, since the foliage 
leaves are themselves held to be sterilised sporophylls. In Chapter XIV. 
it was further concluded (p. 186) that there existed initially only one 
type of leaf—the sporophyll, and that even the protophylls are the 
- eresult of their transformation. Moreover, justification for this is found 
in the positive fact that, spore-production occurs very early in certain 
plants (Ophioglossaceae and some Lycopods), while in Lygodium subalatum 
the extreme condition was actually observed by Prantl, viz. that the 
primordial leaves are themselves fertile sporophylls. With these facts, and 
this general conclusion before us, we may now proceed to consider the 
morphology of the spore-producing members and their relation to the 
other parts of the shoot. 
On an antithetic theory of origin of the sporophyte we contemplate 
an initial condition of a simple body having a coherent group of spore- 
mother-cells, provided, in fact, with a simple spore-sac. The Bryophytes, 
with their concrete archesporium, retain this state even in their more 
advanced forms; but the Vascular Plants, with their discrete sporangia, 
have diverged from it very widely. The two types of construction are 
not gonnected by any living intermediate links, nor is there any direct 
proof that the one type is phyletically related to the other. But both 
provide evidence suggestive of how a segregation of spore-mother-cells 
into distinct sporogenous masses, such as appear in the separate sporangia, 
