224 Mycetozoa of North America 



Genus 38. TRICHIA Haller, Hist. Stirp. Helv. 3: 114. 

 1768. 



Sporangia stalked, sessile, or forming plasmodiocarps; sporan- 

 gial wall membranous or cartilaginous; elaters free, pointed at 

 each end, thickened with two to five spiral bands; spores reticu- 

 late or warted; in the former case the reticulation may be con- 

 tinuous or broken, and forms when seen in profile a border to 

 the spore. 



Type species: Stemonitis Botrytis Gmel. 



Two longitudinal lines are often seen along the middle of the 

 elaters. They signify little except to define the limits of the inner 

 tube of the elater, and will vary in intensity depending on the 

 mounting medium used. They are due to the difference in re- 

 fractive index between what may be in the tube, and that of the 

 material of which the elater is composed. On the elaters of some 

 of the species there will be seen short striae between the spiral 

 bands which appear to be slender ridges. They are placed com- 

 pletely around the elater and parallel. The elaters have spiral 

 bands around them which appear in the field of the microscope 

 as winding in a sinistral direction, that is, like the threads of a 

 left-handed screw. A dextral winding is like that of the threads 

 of a right-handed screw. The use of the words dextral and sinis- 

 tral in a contrary sense is not correct when applied to an object 

 as viewed from the outside. The species of the genus are subject 

 to great variation, much of which is due to their sensitiveness to 

 moisture and changes in temperature while developing. Nearly 

 all of them appear in greatest abundance towards the end of the 

 fruiting season, and are often afi"ected by early frosts. The 

 variations appear principally in the elaters of the capillitium, their 

 length, breadth, branching, netting, terminals, regularity of the 

 bands, and the presence of spines. They may also occur in the 

 stalk, the sporangial wall, or even in the shape of the sporangia. 



Spores more or less completely reticulate. 



Elaters 6-8 /i wide; spores reticulate with narrow bands; 



border 2 ju wide; sporangia sessile. 1. T. favoginea 



Elaters 4-6 n wide; spores reticulate with narrow bands; 



border 1 m wide; sporangia usually stalked, clustered. 2. T. verrucosa 

 Elaters 4-6 yu wide; spores reticulate with broad, pitted 



bands; border 0.5-1 n wide; sporangia sessile. 3. T. affinis 



Elaters 4-6 ;u wide; spores with the reticulations more 



or less broken into shallow, pitted warts; border 



interrupted, 0.5 m wide; sporangia sessile. 4. T. persimilis 



