REDUCTION FOLLOWS DEPENDENCE 239 
podium Selago expands its first leaves as green assimilating leaves, those 
of LZ. clavatum are developed underground, and appear as minute colour- 
less scales, succeeded later by green foliage leaves (Fig. 117). Again, in 
Botrychium virginianum the cotyledon is a green, expanded foliage leaf: 
in B. Lunaria the first leaves are minute colourless scales. These cases 
from among the Pteridophytes illustrate in two distinct series how, wheré 
physiological dependence of the sporophyte is extended, owing to peculiar 
circumstances, a local reduction of its vegetative system may follow. 
They also have their interest for comparison with those Bryophytes which 
have non-functional stomata, for in both the gametophyte appears to 
have assumed increased responsibilities: Nevertheless, in these cases from 
the Pteridophytes, the plant when ultimately 
free shows no general reduction: the effect 
is local, and does not extend to the mature 
organism ; moreover, there is no reason to see 
in such effects any reducing influence upon 
the ultimate spore-output. 
Passing on to the independent sporophyte 
as seen in the Pteridophyta after the embryonic’ 
period is past, two cases require consideration : 
the autotrophic types, on the one hand, and 
on the other those sporophytes which show 
indirect nutrition, such as is seen in the 
mycorhizic types. In independent autotrophic, 
homosporous Pteridophytes, the presumption, 
as has been seen above, would be that they 
would show evidences of amplification rather Kee 
than of reduction. So strong does this pre- ; ; 
sumption appear that, wherever a line of Gitar Baasnauey wae Poors 
2 : w=root; 6/=leaves here represented 
reduction is suggested for a homosporous type, as minute underground scales. 
it should be incumbent upon its author to 
show physiological reasons why it should have occurred. Mere mor- 
phological comparison without physiological support should be held as 
an insufficient basis for theories of general reduction in homosporous 
forms. 
But examples of special reduction, affecting parts or details of 
homosporous Pteridophytes, are not uncommon. It seems not improbable 
that the leaves of modern species of Lguisetum are reduced as com- 
pared with those of early Calamarian forms, and this may be held 
as correlative’ ‘to the development of the cortex in Zguisetum as an 
effective assimilating tissue. Certain of the leaves of Osmunda have an 
arrested lamina, while the leaf-base remains as part of the protective 
armour which covers the axis: potentially these are complete leaves, 
and their arrest before maturity may. be held as a case of reduction. 
Such examples as these are in the nature of correlative adjustment of 
