444 Ganong . — The Comparative Morphology of 
forms the cotyledons are as broad as the hypocotyl and about 
as long, pointed, triangular in section, with the inner line of 
their bases parallel. In all of these characters they show 
resemblance and doubtless relationship with the Opuntiae, 
particularly the Cylindropuntiae, and stand nearer to that 
group than do any other Cactaceae I have studied. As 
compared with Cylindropuntiae, these germinated embryos 
are of smaller size and much more succulent, as is to be 
expected in a group which upon the whole is more xero- 
philous in habit. The resemblance is further increased by 
the common occurrence of axillary buds to the cotyledons in 
Cereus. The epicotyl at first bears the leaves and axillary 
clusters only upon the | system, and the development of 
ribs comes later, one of the cases numerous in this family 
in which phylogeny is repeated in ontogeny. The transi- 
tion to ribs is easy, for these at first are five in number, 
representing of course the vertical orthostichies of the § 
phyllotaxy. 
Another division of columnar Cerei is that including 
C. peruvianus and C . Hystrix (Figs, io and n). In both of 
these the cotyledons are much shorter and somewhat narrower 
than the hypocotyl, and the hypocotyls themselves are com- 
paratively slender. I cannot explain their great deviation 
from the giganteus type except by supposing that the relation- 
ship of these two groups is not so close as has been thought. 
In C. peruvianus the axillary clusters fall into lines, and the 
ribs, usually five, form at once. In the variety monstrosus , 
which reproduces through seeds, the fasciation did not appear 
in seedlings under 2 cm. in height. 
In division B I have had no material, though the C. Emory i } 
figured by Lubbock, belongs here. 
To division C belongs C. Bonplandi (Fig. 12), in which the 
form of the embryo, though not of the adult, suggests relation- 
ship with C. peruvianus and Hystrix. This species shows 
a peculiar feature of the cotyledons, in that one of them is 
always cleft at the tip, and this is rarely the case with both. 
This feature occurs rarely in other species, but this is the 
