MICHIGAN ACADEMY OF SCIENCE. 57 



MICHIGAN SPECIES OF RUSSULA. 



RUSSULA. PERS. 



(From Lat. russula reddish). 



Veil none; the trama of the pileus vesiculose; gills rigid, fragile, without 

 milky juice, acute on edge; spores globose or subglobose, usually echinulose 

 or verrucose, white, cream, ochraceous or yellow. 



Terrestrial, fleshy, putrescent fungi, with a rather glabrous stipe and 

 depressed pileus. 



The pileus may be red, purple, violet, bluish, yellow, green or white. The 

 stem is usually white, sometimes red, or it may be tinged ashy in age. The 

 gills are all shades between shining white and egg-yellow, and this fact 

 illustrates how illogical is our present system of classification among the 

 Agaricaceae. The flesh is composed of large bladder like cells arranged 

 in groups, and surrounded by strands of slender hyphae. Such a structure 

 is said to be vesiculose * and probably accounts for the more or less brittle 

 consistency of these plants. The spores give the characteristic color to the 

 gills, and do not vary markedly in size. The taste, like that of the clo.sely 

 related genus Lactarius is often acrid or peppery, but there are about as many 

 mild tasting species. Milk is lacking, although the gills sometimes exude 

 water. 



The Characters by which the species of this genus are distinguished 

 from each other are of various degrees of constancy and often quite unrelial3le. 

 This is in part due to the fact that the weather, the condition of the soil, the 

 inroads of larvae or old age often change the characters to a considerable 

 extent. The rain may wash off the colors, the hardness of the soil may 

 interfere with their proper development, or they may lose their taste, etc. 

 when too old. The Colors especially are very variable in some species, 

 but as pointed out by Peltereau,t and verified by my own observations, there 

 is always a fundamental color from which the others are derived, so that 

 with sufficient field experience one can recognize a species even under its 

 various color disguises. The Pellicle on the surface of the cap has been 

 much used to separate species. It varies considerably between dry and 

 viscid in different species, or even in the same species under different con- 

 ditions of the weather. With the exception of the first group, it is separable 

 in its entirety or at least in small strips from the margin inwards. On this 

 point the Friesian descriptions of the subgenera are quite misleading, in fact 

 this character is entirely relative. In some species the pellicle or cuticle 

 (as it is indiscriminately called) is a thin, membranous viscid covering which 

 can be peeled off almost entirely; in others we have often a consideral^le 

 adherence of this cuticle, w^hile in the first group the upjjer surface is not 

 much differentiated. The Striations on the margin of the pileus are also 

 of uncertain value for the inexperienced, since even the firm species, of those 

 which possess a pellicle, very often show striations in age. In the species 

 with thin pileus, the attachment of the gills show through as raised lines, 

 which are often tubercular because of the presence of interspacial veins, 



♦Atkinson's Mushrooms page 2.53, fig. 212. (1900). 



tPeltereau Bull. Trimestrial de la Sociciet6 Mycologique. Vol. 24, P. , 



8 



