224 A FREE-LIVING SPOROPHYTE 
each season’s growth, while the tuber itself is here greatly enlarged for 
purposes of storage. The characteristic ‘‘protocorm” is absent from all 
other Pteridophytes. 
The question is, what is the true interpretation of these facts. Does 
the protocorm really represent some condition which existed in the 
phylogeny, intermediate between the fully-rooted sporophyte and that 
more primitive state where it was fully dependent on the prothallus? 
The first point which strikes attention is the way in which the transition 
from dependence to independence of the sporophyte is actually carried 
out in the plants which show this ‘“ protocorm” development: assuming 
that there is some difficulty, nutritive or other, in formation of the root 
itself, the case is quite adequately met by the tuberous development with 
thizoids, as a temporary shift. It seems not improbable that some such 
difficulty should precede in descent the initiation of so important, and so 
characteristic a body as the root. A second point, however, is that a 
protocorm development is exceedingly limited in its distribution among 
living plants: it is not constant even in the genus Lycopodium, and 
outside the Lycopodiales it is not characteristically developed in any 
other of the early forms: this must be taken fully into consideration 
before assigning to the “protocorm” any general phyletic significance. 
But, on the other hand, it may be urged that the real importance of 
the ‘‘protocorm” would exist only in those cases where either the 
root-development has not yet been initiated in the race, or where its 
late development in the individual is a matter of moment, on nutritive 
or other grounds. Immediately any initial difficulty of development of 
a root-system is surmounted in any line of descent, the *‘‘ protocorm” 
would be liable to be cut out of the ontogeny, as a cumbrous and 
unnecessary stage. This would sufficiently account for the absence of a 
‘“‘protocorm” in the great majority of Vascular Plants. But, again, 
Goebel, in arguing against the general phyletic significance of a 
“protocorm,” has cited a number of cases of Phanerogamic Plants in 
which, if the formation of the root is suppressed temporarily or entirely 
in the seedling, a protocorm-like body is formed, which is anchored to 
the substratum by hairs.1 He remarks that this appearance of a 
protocorm in very different circles of affinity seems to him unfavourable 
to the hypothesis of its having a phyletic significance, and he only sees 
in it an organ which corresponds in its development, and especially in 
its formation of roots, to an arrested hypocotylous segment: he suggests 
that a suppression of the formation of the roots may have taken place 
in Lycopodium, as also in the Orchideae, and that this was connected 
with the prolonged development of the germ-plant in them: perhaps 
also the symbiosis with fungi which takes place in these plants, may 
have had its effect. On this view the ‘ protocorm” would be secondary, 
and it would not illustrate an archaic mode of establishment of the 
 Organography, vol. ii., Engl. ed., p. 232 
