Pa eae CHAMBERLAIN—CERATOZAMIA 17 
before the stage shown in figs. 20-23 is reached, and consequently 
before the cotyledons have begun to be differentiated. Sister 
HELEN ANGELA (14), noting this fact and finding traces of vascular 
tissue which might belong to the missing cotyledon, rotated seeds 
on a klinostat from the time the seeds were liberated until the 
embryos were mature. Such seeds showed two cotyledons as in 
other cycads, so that the single cotyledon of Ceratozamia, as it is 
found in nature, is due to a suppression of one of the cotyledons, 
doubtless on account of the early liberation of the seeds. 
The seeds of Ceratozamia germinate as soon as they are ripe, 
a feature which I have noted in Dioon edule, D. spinulosum, Zamia 
floridana, Cycas circinalis, Macrozamia Fraserit, and Stangeria 
paradoxa. Very probably the seeds of all cycads may germinate 
without any resting period; but seeds of Ceratozamia, which had. 
become dry in the laboratory, were planted a year later and germi- 
nated readily. Seeds of Dioon edule which had been in the labora-” 
tory for nearly three years germinated. The most favorable time 
for germination is that immediately following maturity, for at 
this time nearly all seeds of both Ceratozamia and Dioon will 
germinate, but after a lapse of a few months the proportion of seeds 
which will germinate steadily diminishes. 
Summary 
1. Ceratozamia mexicana grows best in well shaded mesophytic 
conditions. 
2. Any individual in passing from the seedling to the adult 
stage shows such a progressive change in its leaves, the leaflets 
becoming larger, broader, thicker, and more numerous, that descrip- 
tions of species based largely upon leaves are open to suspicion. 
3. The ovulate strobilus shows considerable variation in the 
size and number of its sporophylls. 
4. In addition to the primary haustorium, a system of secondary 
haustoria is developed later from the basal portions of the pollen 
tube. There are regularly two sperms, but occasionally four are 
produced. 
5. A small ventral canal nucleus is present, but occasionally 
it enlarges and may fertilize the egg. It is suggested that this 
or 6 
