198 BOTANICAL GAZETTE [MARCH 
in one case. In most of these cases the 12 chromosomes were visible 
in one section 3 to 5 » thick (jig. 45), but in a few cases the sections 
on either side had to be examined and drawings made to determine 
the actual number of chromosomes. This in every case changed 
what would have been a count of 6 or 8 to 12. GUIGNARD (12) found 
8 chromosomes in the pollen mother cells of Ceratozamia; and OVER- 
TON (13) found the same number in a count of the chromosomes 
in the endosperm cells of the same species. In the 25 nuclei of 
Zamia floridana counted, 12 chromosomes were found; and CHAM- 
BERLAIN (27) gives the same number for Dioon edule. 
Most of the stages in the development of the tetrad were seen in 
Zamia, and they followed closely the figures of JURANYI (4) and 
TReEvuB (8). In most of the tetrads the ring of cellulose was not seen 
all the way across the cell until the four daughter nuclei were clearly 
outlined and the cell plate between them had commenced to grow. 
In Zamia floridana the output of spores per sporangium is about 
500 or 600; in Ceratozamia mexicana 8,000; and in Encephalartos 
villosus 26,000. This makes the output per sporangium in the few 
species examined increase according to the number of sporangia to 
the sporophyll. The number of observations, however, is too small to 
furnish a safe basis for conclusions. Among the Marattiaceae the lar- 
gest output is for Kaulfussia (7,850); and in Isoetes SmiTH (18) esti- 
mates several hundred thousand spores in a single microsporangium. 
THE MALE GAMETOPHYTE 
The strobili of Zamia received from Florida the first of February 
were about ready to shed the pollen, which was in the three-celled 
stage. At the first observed division of the spore the prothallial 
cell is cut off, lying against the wall of the spore, with its inner face 
arching almost into the center of the spore (jig. 46). At the next 
division the generative cell is cut off (fig. 47), its nucleus being some- 
what flattened and deeply staining. The tube nucleus is very large, 
stains less deeply, and lies generally in line with the other two. 
A to per cent. sugar solution, sterilized and kept in sterilized 
dishes, was favorable for the growth of the pollen tubes. Some of 
the solutions containing pollen grains were kept in an oven at a temper- 
ature of 28° C., while others were kept at 21° C., the temperature of 
the room. In forty-two hours the tubes in the oven were two or 
