EXCLUSION OF CERTAIN FACTORS 131 
occurred in various instances, and in any given case the proper initial 
attitude is to hold that either mode of origin may have been the source 
of the synangial state as it now appears. 
The feature which has probably been most effective of all in distracting 
attention from the methodical analysis of the polysporangiate state in 
Vascular Plants at large has been the swamping effect of continued apical 
growth, and of branching. In the lower Vascular Plants both apical 
growth and branching may be seen in either the sterile or the fertile 
regions. In the higher Flowering Plants the floral region itself is 
characterised by absence of branching, and by restriction of apical growth, 
but both occur freely in the sterile region of the inflorescence. The 
results of this in the Flowering Plants are apt to be so dominating that 
it is often hard to recognise the small terminal and late-produced strobilus 
or flower as the actual residuum which progressive sterilisation and growth 
of the sterile tract have left. 
Among Vascular Plants it is only in the simpler Pteridophytes that this 
aspect of the sporophyte generation clearly emerges: and this is largely due 
to the fact that in them branching of the axis is often less profuse, or may 
even be absent altogether: moreover, the structural similarity between the 
sterile and fertile regions suggests their comparison. As a consequence of 
such compari-ons, it follows that the great disproportion of the two regions 
so often seen in the Flowering Plants may be discounted as a secondary 
effect: it has been brought about principally by continued apical growth 
and repeated branching in the vegetative region, together with higher differ- 
entiation of the sterile and fertile shoots. Maintaining consistently this 
point of view, the overpowering effects of continued apical growth and of 
branching will be estimated at their right value, and so the way may be 
prepared for a more exact enquiry into the origin of the polysporangiate 
state, even in the more advanced types. It is by some such analysis as 
that sketched in this chapter that it may be possible to attain to a 
reasonable opinion how the condition, seen in the earlier Vascular Plants 
came into existence. The detailed practical application of the method may 
often be difficult, and only partially successful: the present object has been 
to lay the basis for such an analysis, by showing what the recognised 
factors of numerical change of sporangia actually are, and to simplify the 
problem by showing that certain of those factors are of limited application 
only. 
