1912] CHAMBERLAIN—CERATOZAMIA 9 
dichotomously and occasionally anastomose. The number of 
bundles in the outer system varies from 8 to 10, with 9 as the most 
usual number. About 6 bundles pass through the stony layer to 
the inner fleshy layer, where they branch repeatedly. In the stalk 
of the sporophyll there is a single bundle passing toward each ovule; 
this bundle branches once in the spreading part of the sporophyll, 
and each branch contributes to both the inner and the outer vascu- 
lar systems of the ovule. 
Both strobili and ovules may reach the maximum size in green- 
house specimens where there has been no possibility of pollination. 
This seems to be the rule in Ceratozamia, although I have seen two 
or three greenhouse strobili in which nearly all the ovules were 
abortive. 
The male gametophyte 
Records in regard to the time of shedding pollen are not very 
complete. In two staminate cones sent from the Almolongo Valley, 
near Jalapa, December 5, 1906, arriving in Chicago December 12, 
the pollen tetrads had already shaken apart, but the exine had not 
begun to look yellow. In two cones sent from the same place 
February 5, 1907, and reaching Chicago 7 days later, the pollen was 
yellow, but the sporangia had not yet dehisced. Four cones from 
Chiltoyac, near Jalapa, reached Chicago March to, 1906, and the 
largest of the four began to shed its pollen 2 days later. A cone of 
Ceratozamia mexicana var. longifolia, sent on April 14, 1909, from 
the Missouri Botanical Garden by Professor TRELEASE, reached 
Chicago the following day. Much of the pollen was already shed. 
While there is considerable variation in the time at which the 
pollen is shed, the condition of the pollen at the time of shedding is 
always the same; there is a tube cell, a well developed, persistent 
prothallial cell, and a generative cell which will later give rise to the 
stalk and body cells. 
The mature pollen grain of Ceratozamia mexicana can be dis- 
tinguished from that of Dioon edule by the spore coats, the exine 
and intine being quite uniform throughout in Ceratozamia, while in 
Dioon the exine is much thicker at the base of the spore and the 
intine much thickened along the sides. 
The pollen grain, as it is shed, is shaped like a kernel of coffee, 
