3^9 
Reply to Criticisms. 
though incapable of assimilation by its leaves, is still able to 
support the growing embryo of a relatively large sporogonium ? 
It is possible, as Professor Goebel suggests, that the required 
organic supply is entirely derived from the assimilative activity 
of the protonema ; but in presence of such a peculiar physiolo- 
gical condition as that above noted, I think that more exact 
proof of the mode of nourishment of Buxbaumia will be neces- 
sary before the facts relating to it can be accepted for purposes 
of morphological argument. I find it difficult to believe that 
we really see a primitive condition in a plant in which the 
leaves are incapable of assimilation themselves, though the 
plant receives its support indirectly through them, from out- 
growths of a filamentous character, formed, comparatively late, 
from their margins. Whether the organic supply be exclu- 
sively derived from the assimilative activity of the green 
filaments or in part derived saprophytically from the sub- 
stratum, the indirectness of the mode of supply, and the late 
appearance of the parts which supply it, are facts not easily 
reconciled with the suggested primitive character of the 
organism. 
Nor does the comparison with Diphyscium appear to me to 
strengthen the case : the relations of these genera are not very 
close, though the similarity of their sporogonia is greater than 
that of their gametophytes. It is true the seta of Diphyscium 
is short (but I do not see that this is a fact of material weight), 
while that of Buxbaumia , the supposed more primitive form, 
is long. In Diphyscium the relatively large green leaves of 
the female plant have not the marginal protonema as in Bux- 
baumia : on this ground, as well as from the green colour of 
the leaves — that is, on grounds of directness of nourishment — 
Diphyscium would appear to me to be the more primitive form. 
The relatively large bulk of the rhizoids to the bulk of the 
plants in both B. aphylla and D . foliosum is certainly striking ; 
also the exceedingly fine, hypha-like ramifications into which 
they run, and their very complicated anastomoses, so as to 
form a plexus extending far into the substratum. I have 
also noted a frequent, though not constant, association of 
