LEVINE: CYTOLOGY oF HYMENOMYCETES 175 
g. The centrosomes mark the points of origin for the sterig- 
mata. They are carried up with the growth of the sterigmata 
and into the spores. They also apparently determine the apex 
of growth of the spores. 
10. The spores in all the forms studied are uninucleated at 
first. The primary spore nucleus divides at once. The kary- 
okinetic figures are small but very sharply differentiated with well- 
developed centrosomes and polar asters. In the spores of B. 
albellus a second division occurs. 
11. In Boletus chrysenteron, B. punctipes, and B. griseus, basidia 
with mature sterigmata are found before the completion of the 
second division. Normal basidia are also present. 
12. An alternation of generations comparable to that in the 
Uredineae is also present in the Basidiomycetes. The sporophyte 
begins at some indefinite point in the mycelium and extends 
through the development of the carpophore. 
COLUMBIA UNIVERSITY, NEw York. 
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