I20 



MORPHOLOGY OF GYMNOSPERMS 



spherical, and because the formula 

 between spores, but the error is far 



^'.^^^y 



'^'- 0¥' 



Fig. 1 10. — Dioon edide: microspo- 

 rangium; detail showing thickened epider- 

 mis, wall cells, tapetum, and sporogenous 

 tissue; X250. — After Chamberlain (63). 



does not regard the small spaces 

 less than the variation in the out- 

 put of individual sporangia of 

 average size. It is recognized 

 that this formula could be used 

 only when spores are very small 

 and sporangia very large. Esti- 

 mating in this way. Chamber- 

 lain (63) found the output of 

 spores in Dioon edule to be 

 30,000; Miss F. Grace Smith 

 found it to be 26,000 in En- 

 cephalartos villosus, 8,000 in 

 Ceratozamia, and 500-600 in 

 Zamia floridana. In general 

 the results favor the view that 

 the output is larger in the more 

 primitive forms and decreases 

 toward the more highly special- 

 ized forms. 



Fig. III. — Dioon edide: microsporangium; two of the sporangia of a sorus, 

 showing extensive sporogenous tissue and scanty tapetum; two-celled hairs growing 

 on the base of the sporangium; X5S. — ^After Chambeklain (63). 



Since the spore is regarded as the first cell of the gametophyte 

 generation, it will be considered in the section on the male gametophyte. 



