334 BOTANICAL GAZETTE [way 
meristems was shown by Bower to possess considerable phyloge- 
netic value, in the case of ferns, and to lead to results which 
agree with those arrived at by a comparison of other characters. 
The fact that Bower has since changed his view with regard to 
which type of fern is more primitive does not in any way lessen 
the value of his previous conclusions, If we extend the series 
made out by him it would be in this order: typical leptosporan- 
giate ferns, Osmundacee, eusporangiate ferns, Selaginella, Iso- 
etes, and Lycopodium. In this connection the dichotomy of the 
roots of Isoetes, Lycopodium, and Selaginella ought not to be 
overlooked. 
The ligules of Selaginella and Isoetes were by Goebel made 
the ground for grouping the two genera into one order, the 
Ligulate, though the classification was recognized by its pro- 
poser as merely one of convenience. In the former part of this 
paper I have made a comparison of these organs, and expressed 
the view that their similarity is sufficient to demonstrate their 
homology. If this view is correct, it furnishes additional sup- 
port to the relationship of Isoetes and the Lycopodiales, 
especially in consideration of the discovery of a ligule in the 
vegetative leaves and the sporophylls? of Lepidostrobus, another 
lycopodiaceous plant. : 
Turning now to the gametophytes, we notice that when Vines 
suggested the connection of Isoetes and ferns, it was supposed 
that important differences existed between the female gameto- 
phytes of Isoetes and Selaginella; but the later and more com 
plete investigations of Heinsen (1) and Arnoldi (1) have demon- 
strated their close resemblance. The diaphragm of the female 
gametophyte of Selaginella is not a true septum, and does not 
arise as Pfeffer (1) supposed it did, by the division of the pues 
into two cells. In both Isoetes and Selaginella, the free seis’? 
nuclei, their parietal placing, and the gradual extension of ve 
division from the periphery to the center of the spore are t : 
same, and have no counterpart in the germination of the ii 
spores of heterosporous ferns. The gametophytes agree also! 
the absence of chlorophyll. 
? Maslen (1). 
