24 The Botanical Gazette. {January. 
prothallia of the Polypodiacee, Cyatheacee and Schizza- — 
cez, in which the first product of germination isa filamentous _ 
structure afterwards developing into a cordate thallus, or the — 
rather poorly understood prothallia of the Ophioglossee may 
be considered as dimorphic gametophytes and interpreted 
accordingly. It will be seen, however, that protonemal and 
metanemal stages would in such case be analogous (not 
homologous) tothe protonema and metanema of the Muscinea, 
offering a case of parallel development under similar phys-_ 
iological conditions. And under the methods of classifica~ 
tion proposed it is apparent that the conclusions’ of Goebel?’ 
can not yet be accepted. As to whether ‘‘we may regard as 
the starting point for Bryophyta and Pteridophyta alga-like 
forms consisting of branched filaments,” judgment must, I 
believe, be suppressed for the present. It must first be de- — 
termined whether the prothallium of the fern which is to be- 
taken for the basal fern corresponds with algal archenema oF ~ 
with the protonema or metanema of the Muscinee. . 
Conclusion.—The gametophytic structures below the ferns — 
may be described under the heads of archenema, proton r 
and metanema. 
It has not yet been clearly shown with which of these three 
series the fern prothallium is homologous. 
Until the exact homologies of the fern prothallium are dist Y 
covered, under such a classification it will not be possible to | 
make full use of gametophytic stages in fern phylogenesis. — 
Phylogenetic argument based upon previous interpretations a ; 
of the fern gametophyte may be considered as open to pos- @ 
sible emendation. a 
University of Minnesota. 
— 
= 
Bynes 
a ee ee 
— a 
®*Goebel, Zur Keimungsgeschichte einiger Farne. Ann. Buitenz. 7: 74. 1887. 
