238 AMPLIFICATION AND REDUCTION 
Among the Mosses the small Cleistocarpic forms are virtually dependent 
for all their nutritive supply upon the Moss-Plant. In larger forms, such as 
Mnium, Splachnum, and Buxbaumia, there is a well-developed assimilatory 
system with functional stomata, and there is no doubt that it con- 
tributes materially to the nutrition of the sporophyte. But in some cases, 
such as Sphagnum, Ephemerum, and Nanomitrium, stomata, though present, 
are non-functional, a fact which indicates a probability that thesé sporo- 
gonia are now more dependent for nutrition upon the Moss-Plant than 
their ancestors were. There seems some probability also that there has 
been, in the genera last named, a reduction in the numerical spore-output. 
These examples from the Bryophyta illustrate how the sporophyte is 
variously dependent upon the gametophyte for nutrition ; and that while 
2950 SOQ, BN 
Ova PO 
o8o03 90 aoe N 
ro) we 
SQ OG F090 | 
Bs. 
Fic. 116. 
Longitudinal sections through sporogonia of Cyathodium cavernarum (A), and Cyatho- 
dium foetidissinum (B), to show their position on the thallus and their relative size. In 
both cases the sporogonia contained spores and elaters with their walls thickened, but had 
not quite attained their full size. x74. (After Lang.) 
e 
in some cases provision has been made for some degree of self-nutrition, 
in others the dependence may have increased in the course of descent, 
as shown by reduction of the assimilatory system of the sporophyte; and 
there is also some indication that the spore-output has suffered by the 
change. Thus, notwithstanding their homoporous state, it would seem 
probable that phyletic reduction both of the vegetative system and of the 
spore-output has been operative among them in some cases in their 
neutral generation. 
Among the Pteridophytes the embryonic dependence is usually brief: 
the young plant hastens to elaborate its own assimilatory system, and to 
become physiologically independent, as in any mature Fern, or Horsetail. 
But under some circumstances the period of dependence is liable to be 
extended, a condition which brings with it evidences of a corresponding 
reduction of the first-formed appendages. This is seen in certain embryos 
borne on underground, mycorhizal prothalli, and examples of it are seen 
in the Lycopods, and in the Ophioglossaceae. For instance, while Lyco- 
