88 
BOTANY: C. J. CHAMBERLAIN 
tions which one sees in museums bring to mind the so-called ferns of 
the Paleozoic. However, some of the living genera are distinguishable 
in the Tertiary and it is possible that the family goes back even to the 
Triassic. The resemblance of the stems and leaves of the living cycads 
to those of the Bennetti tales is too striking to be accidental; on the 
other hand, there is nothing in the seed-bearing cones of any of the 
Bennettitales yet described which could have given rise to the seed- 
bearing cones of the living cycads. Further investigation, especially of 
Triassic forms, must be made before one can say with any confidence 
whether the modern cycads have come from the Bennettitales, or both 
have come from the Paleozoic Cycadofilicales. 
The geographic distribution of the Hving cycads is very restricted. 
All are tropical or subtropical. Four of the nine genera belong to the 
western hemisphere and five to the eastern, there being no genus common 
to both hemispheres. With two exceptions, the genera are very local 
in their distribution. In the western hemisphere, the thirty-odd species 
of Zamia range from Florida to Chili; while, in the eastern hemisphere, 
the dozen species of Cycas range from Japan to Australia. Two genera 
are found only in Mexico; one only in Cuba; two only in AustraHa, one 
of these being confined to Queensland; and the other two are found 
only in South Africa. So, with the exception of the two genera which 
cross the equator, the western genera are in the northern hemisphere 
and the eastern genera are in the southern. Even in the places men- 
tioned, the plants occur singly or in scattered groups. There is no such 
things as a cycad forest. 
Perhaps, later, it may be possible to give some reason for this peculiar 
distribution and for the scarcity of individuals. 
The nine genera of hving cycads are so sharply defined that there is 
no difficulty in recognizing them. In herbarium specimens, this rigidity 
extends to species, and, before I began to study cycads in the field, I 
supposed that the species were rather sharply marked. By the time I 
had made four excursions into the Mexican tropics, it was evident that 
species could vary, even in Dioon and Ceratozamia. However, I was 
not prepared for the bewildering maze of forms which I found as I 
tramped the Macrozamia regions of AustraHa. Three species, with erect 
cylindrical trunks, are easily distinguishable, but I was almost tempted 
to say, ^'Call the rest Macrozamia spiralis, and let them go." Taxono- 
mists describe several species of the South African genus, Stangeria, 
but, after wandering over nearly the entire range of the genus, from 
Zululand to Port Elizabeth, I should not be surprised if all of them should 
be raised from the seeds of a single cone. Some species of the African 
