ORDER AGARICALKS 501 



Many Agaricaceae show clamp connections at the septa of almost all 

 the hyphae of the lamellar and pilear trama, the cortex of the pileus, and 

 the tissues of the stipe as well as the mycelium from which the spore fruit 

 arose. In many cases the clamp connections occur only at occasional septa 

 and only in special portions of the pileus or stipe, often only in the cortical 

 regions. In Russula and Lactarius groups of spherical cells (sphaerocysts) 

 are found in the pileus and even in the lamellae in addition to the usual 

 slender hyphae. The pilear trama of other genera may show enlargements 

 of the hyphae but not so characteristic as those of the genera mentioned. 

 Slender hyphae bearing clamp connections frequently do not develop 

 these structures where cells much larger in diameter are developed as they 

 grow. In the genus Lactarius the tissues of the pileus, stipe and gills 

 possess branching hyphal tubes filled with latex which flows out of breaks 

 in the tissue and coagulates. The fresh latex may be white, pink, yellow, 

 green, blue, or even colorless. It may change color on exposure to the air 

 or remain unchanged. Aside from the protection to wounds afforded by 

 the coagulated latex it may be that the laticiferous tubes serve for food 

 transportation. Besides this genus laticiferous vessels are reported by 

 Heim (1936b) in three other genera of Agaricaceae from Madagascar, 

 Bertrandia, Mycena, and Rhodophyllus, as well as in some species of 

 Gasteromycetes. 



The species of Agaricaceae may be " homothallic " or " heterothallic " 

 and bipolar or quadripolar. Most genera of the Agaricaceae have not been 

 grown in culture so that it is not known how extensively the appearance of 

 two or more sexual phases is to be found. The phenomena of sexuality 

 have been discussed rather fully in the preceding chapters. Oidia are pro- 

 duced in abundance in monocaryon cultures but are usually absent from 

 dicaryon mycelium. Where they do occur, as Vandendries and Martens 

 (1932) described for Pholiota aurivella, they may be binucleate and give 

 rise to dicaryon mycelium or divide into two uninucleate cells which give 

 rise to monocaryon mycelium. 



The Agaricaceae are mainly saprophytic, living on the ground, decay- 

 ing leaves, bark, wood, manure, etc. Some species of Nyctalis and Volvaria 

 are parasitic on other Agaricaceae. Armillariella mellea (Vahl) Karst. 

 {Armillaria mellea) attacks the roots of trees and kills their cortical tissue, 

 growing up in the living portions of the bark of the tree trunk and causing 

 the death of the tree. It is especially destructive to apple and cherry trees 

 planted where previously there were oaks or other trees on whose roots 

 this fungus once grew parasitically, continuing to live as a saprophyte until 

 the apple or cherry roots became available. Agaricus campestris L. ex Fr. 

 and one or two other species are cultivated for food and many wild species 

 are collected for this purpose. Buller (1922) pointed out that Marasmius 



