1908] CURRENT LITERATURE 57 
Running throughout the hypothesis is the assumption that the most critical 
and hence controlling fact in the life of any organism is the relation existing 
between environment and fertilization. Perhaps the most fundamental con- 
ception is that the “‘Archegoniatae” are amphibious. (It may not be out of place 
here to suggest that the group name ‘“‘Archegoniatae” has about outlived its 
usefulness. To associate the widely separated bryophytes and pteridophytes 
in this way, and to include or exclude part of the gymnosperms, is a grouping 
too unnatural and misleading to be continued.) That the gametophyte of 
“Archegoniatae” is amphibious means that it is just as aquatic as an alga, and 
shows this in its delicate structure, lack of intercellular spaces, lack of a water- 
conducting system, and the possibility of fertilization only in the presence of 
water. ‘The gametophyte proclaims its ultimate dependence on external fluid 
water as thoroughly as an alga.’’ On the other hand, the sporophyte is char- 
acteristically an aerial body, with its more robust habit, ‘‘ventilating”’ system, 
vascular strands, and spores adapted for dryness. 
Attention is called to the fact that the ‘‘Archegoniatae”’ retain with remark- 
able pertinacity this “awkward and embarrassing” method of fertilization; but 
that with the advent of the seed plants this becomes modified, and the higher seed 
plants at last become completely terrestrial. 
A general outline of the steps by which the sporophyte was established and 
amplified as a terrestrial structure may be stated as follows: The gametophyte 
was the previously existing phase, and the initial step in the appearance of the 
sporophyte was the “‘post-sexual divisions, giving rise to a plurality of germs,” 
such as is observed in the life-histories of certain green algae. In plants exposed 
to changing conditions of moisture and drought the fixing of such a generation 
would be assured, according to the following logic: external water would be occa- 
sional rather than constant; hence the sexual act would be occasional; hence 
there would be less dependence upon the sexual act for multiplying individuals; 
hence a “premium would be put upon” the other method of propagation suit- 
= for drier conditions. Thus the sporophyte is to be rec gnized as a body 
originating as an adaptation to terrestrial life. 
In amplifying the sporophyte, it is assumed that the first and also the final 
office of the sporophyte is to produce spores, and that the larger the number 
of spores (in homosporous forms) the better the chance of survival; therefore 
the increase in number of spores is ‘‘encouraged.” But to protect spores when 
A and to nourish them during development presupposes some vegetative 
em. 
The process for developing this vegetative system is the familiar theory of 
Progressive sterilization, so well traced by the author among bryophytes. Among 
Tyophytes, however, there are certain limits imposed by mechanical and physi- 
ological conditions; while among vascular plants there is greater freedom for 
Progress, chiefly by the segregation of the sporog ee 
and the formation of ‘‘appendicular organs.” As a result of this progressive 
Sterilization and n g £48 fc Meet as the fertile tissue appears later and 
o 
