242 AMPLIFICATION AND REDUCTION 
end in itself, but only a means to the end, viz, the suitable nutrition 
of the nascent germs. There are several ways in which this nutrition 
may be effected; they are these: 
(1) Nutrition by the gametophyte, which was the most primitive 
method. 
(2) Self-nutrition of the sporophyte by its own assimilatory system. 
(3) Indirect nutrition of the sporophyte, e.g. by mycorhiza. 
Provided the spore-production be maintained, it matters not which of 
these is effective, or dominant in any individual case; and in point of 
fact they have varied in the phyletic history. In the original state of the 
sporophyte there was undoubtedly nutrition by the first method. Subse- 
quently the second supervened ; and there is reason to think that during 
the phyletic history there has been a varying balance of the effectiveness 
of these two factors. Generally speaking (1) has waned in importance 
proportionately to the whole requirement; but in such cases as the 
Moss-sporogonia with non-functional stomata, and in the large under- 
ground prothalli of Lycopods and Ophioglossaceae (1) appears again to 
have increased in proportional importance, encroaching upon the effective- 
ness of (2), with the result that local reduction of the mechanism of 
self-nutrition in the sporophyte followed; but still that may have pro- 
duced no ill-effect upon the spore-output. Passing to the independent 
sporophyte, its primitive nutrition was autotrophic (2), and there was a 
suitable balance of the nutritive and propagative systems, the method of 
which differed in the different phyla. Lastly, in those cases where 
indirect nutrition (3) by mycorhiza contributes effectively, a reduction of 
the normal nutritive system of the sporophyte may take place; but so 
long as the sum of nutrition is maintained the propagative system would 
not be reduced. If, however, for any reason the sum of nutrition fall, 
then general reduction would ensue. 
It is not then enough to suggest reduction on mere grounds of com- 
parative convenience: to make the suggestion convincing in any group 
where general reduction is believed to have occurred, it will be necessary 
to prove that the sum of nutrition, from whatever source, has diminished 
in the course of descent, and that reduced spore-output has been the 
result. Until this has shown to have occurred in any case, there seems 
no sufficient reason to accept as more than a quite open hypothesis any 
suggestion of general reduction of its sporophyte. The biological probability 
is against extensive, or general, reduction in homosporous forms, and in 
any case the positive balance during the whole phyletic history must 
have been on the side of amplification. 
But where there is heterospory, and especially in plants showing the 
seed-habit, where a high certainty of a germ becoming effectively established 
is attained by storage in the enlarged spore, reduction in the number of 
spores followed, and the cognate reduction of other parts assumed many 
