336 BOTANICAL GAZETTE [May 
one, due to the late differentiation of the embryonic organs 
and the suppression of the stem, rather than to any deep-seated 
likeness. However that may be, the suspensor of Lycopodiumand 
Selaginella is a positive morphological character separating them 
from Isoetes. Probably the embryos of Isoetes and Botrychium 
can be looked uponas generalized types, the specialization taking 
the form in ferns of a very early demarcation of the embryonic 
organs, and in Lycopodium and Selaginella of a suspensor. 
Two other possible reasons for relating Isoetes to ferns 
deserve a passing mention. Of the connection between the 
velum and the indusium enough has already been said; and of 
the agreement of the stems of Isoetes and Botrychium it is suf- 
ficent to say that the agreement is simply in the fact of second- 
ary thickening. 
The claim that Isoetes is the genus of modern pteridophytes 
which makes the closest approach to angiosperms, particularly 
to monocotyledons, gives it an interest quite out of proportion 
to its numerical representation. It is not clear, however, that 
the claim is well supported by facts. Unquestionably Isoetes 
and Selaginella, in their heterospory, and their intrasporic and 
reduced gametophytes, exhibit features of life history which 
run closely parallel to that of seed-plants ; but such features 
really foreshadow monocotyledons no more than they do other 
seed-plants. The hypodermal archesporium, and the origin of 
the megaspore mother cell as the lowest of a row resulting from 
periclinal divisions of an archesporial cell—two points which my 
observations disprove — would, if established, be as strong proof 
of a gymnosperm as of an angiosperm attachment. Some facts 
distinctly favor the gymnosperm connection; these are the a 
ner of germination of the megaspore, and the method of selection 
of the megaspore out of a large mass of potentially spore 
producing cells, as in Cycas, Callitris, etc., to which may be 
added whatever favors the relationship of Isoetes with the Lyco- 
podiales. 
Professor Campbell has shown that the embryo of Isoetes 
bears a likene&8s to that of a monocotyledon in having a lateral 
