KUNKEL: PROMYCELIUM OF CAEOMA NITENS 363 
The sterigma arises as a pointed outgrowth from a promycelial 
cell. It tapers evenly and is generally slightly curved rather than 
straight. Its diameter at the base varies between three and five 
microns, while at the tip its diameter measures from one and one 
half to two and one half microns. It normally reaches a length 
of from fifteen to twenty microns, but in some cases it becomes 
much longer. 
The sporidium, as is the rule in the rusts, is a typically kidney- 
shaped spore, slightly narrower at its basal than at its distal end. 
Maturing in a short time after the aecidiospore begins to germinate, 
it soon falls off from its sterigma and, on a moist surface, germinates 
Fig. 1. 
mycelium; d, aecidiospore producing an abnormal promycelium; ¢, germ 
aecidiospore with promycelium bearing sporidia in different stages of development. 
in a few hours. Sometimes it produces a secondary sporidium, 
but more often it may develop a corkscrew-shaped germ tube that 
frequently reaches a length eight or ten times that of the sporidium. 
Occasionally this germ tube shows branching. The diameter of 
this germ tube is always much less than the diameter of the nor- 
mal promycelium. 
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