‘CHAPTER X. 
VARIATIONS IN NUMBER OF SPORANGIA. 
NOTWITHSTANDING the familiarity of the fact that the polysporangiate 
state is the constant condition in Vascular Plants, little attempt has 
hitherto been made to analyse the methods of variation in number of 
the sporangia which they bear. But this would appéar to be a promising 
line of enquiry, for it may be held that an adequate knowledge of the 
methods of variation seen to be actually operative now should throw light 
upon the factors which have been operative in. the past, and thus some 
suggestion should be obtained how the divers polysporangiate types came 
to be as we now see them. To such an end the facts drawn from those 
organisms which are held to be relatively primitive, such as the homo- 
sporous Pteridophytes, will naturally bear greater weight than those derived 
from more recent and specialised forms, such as the Flowering Plants. 
Nevertheless it will be best to treat the question of change of number of 
sporangia first of all in its relation to the Vascular Plants as a whole, 
so that all the known factors may be disclosed: and it will be a matter 
for subsequent discussion to decide in any individual case which of those 
factors appear to have been operative in bringing that organism to its 
present condition. 
' The subject of variation in number of sporangia in the individual or 
the race may be discussed either from the physiological or from the 
morphological point of view: it is the morphological question which will 
now be brought forward, though always in the light of physiological con- 
siderations. But I wish at once to meet the objections of those who 
will say from the physiological side that the number of sporangia depends 
on nutrition: this self-evident proposition neither explains nor rules out 
the morphological question how a plurality of sporangia arose, nor how 
the great numerical differences which we see may have been attained : 
nor does it modify the effect which observations of their numerical change 
in the living individual, species, or genus may have on views of Descent 
of the plants observed. By such observation and comparison of living 
