195 
Apogamy in Ferns . 
conceivable, though as we think improbable, that Dictyota may afford 
a true example of homologous alternation ; this would not, however, affect 
the question of the origin of the sporophyte in the Archegoniatae . 1 * * 
In the Desmids and the Conjugatae, as Klebahn and others have 
shown, there exist tolerably conclusive reasons for believing that meiosis 
occurs immediately on the germination of the zygote, and that conse- 
quently the whole plant belongs to the postmeiotic stage of the cellular 
cycle, thus forming the exact antithesis of what occurs in Fucus . 
Once more, Allen has shown in Coleochaete that meiosis is bound 
up with the first two divisions, that is with the germination, of the zygospore. 
Consequently, the cells of the 4 sporophyte ' organism lying within the 
oogonium belong to the postmeiotic cell generations. But the ordinary 
Coleochaete plant only arises from the zoospores which are produced by 
this ‘ sporophyte.’ But in spite of this early onset of meiosis probably few 
would refuse to admit the claim of the f sporophyte’ of this plant to be 
regarded as an intercalated cell series. The Coleochaete plant is not 
formed till the emitted zoospores give rise to it, and the cell divisions which 
intervene between zygosis and their formation can hardly be looked on 
as other than a new and intercalated development. It is not very likely 
that any one would maintain that the sporophyte was the modified repre- 
sentative of a normal Coleochaete plant, whereas it is easy to see how it 
might have arisen on the lines of Oedogonium or Sphaeroplea. 
But the fact that in Coleochaete the ‘ sporophyte,’ after it has passed 
the first stages of germination, should consist of postmeiotic cells affords 
an interesting contrast with what happens in the Archegoniatae. In both 
cases the spore (or zoospore) marks the natural transition to the gameto- 
phyte, and since we find that meiosis is not of necessity bound up with 
uniform stages in the life-history of all organisms, there appears to be little 
justification for a refusal to admit the claims of Coleochaete to be regarded 
as a type of alternation on all fours with, though forming a variant of, that 
exhibited by the Archegoniatae. We frankly confess that such a com- 
parison appears to us more probable than a view which would relegate 
the postmeiotic cell-generations to a position analogous to that of the 
protonema of a Moss. 
Finally, the flowering plants themselves afford perhaps the best proof 
of the statement that whilst meiosis is of fundamental physiological im- 
portance it is nevertheless not bound up with definite morphological 
limitations. In the majority of cases, it is true, it does coincide with the 
onset of particular morphological changes, but it is really independent 
1 Recent investigations have shown that in the relation of the incidence of the meiotic phase 
the Florideae, in which there are cogent reasons for admitting the existence of a true alternation of 
generations, resemble the lower members of the archegoniate series. Cf. Yamanouchi, The Life- 
history of Polysiphonia , Bot. Gazette, vol. xlii. 
