DEPARTMENT OF BACTERIOLOGY. 195 



rooms, but recognizes the fact that some are poisonous and 

 others are not, just as is the case with higher plants. Mush- 

 rooms belong to that great class of plants known as fungi, 

 which differ from ordinary plants in their shape, color, and 

 mode of life. They consist of a vegetative part and a re- 

 productive part. The vegetative part is usually inconspic- 

 uous and simple in structure, consisting of a mold-like mass 

 of minute colorless threads known as the mycelium, which 

 grows on decomposing vegetable matter on the surface of 

 the soil or on dead trees. The reproductive part is by far the 

 largest and most conspicuous part, and is what is commonly 

 called the mushroom. It assumes various forms, the most 

 common of which is the familiar umbrella shaped structure 

 consisting of a stem, and an expanded portion called the 

 pileus or cap. The under side of the cap is covered either 

 with thin radiating plates called gills, or with minute closely 

 packed tubes or pores. On the surfaces of the gills or in the 

 cavity of the pores the reproductive bodies or spores are 

 borne. In some species in the young state the gills or pores 

 are covered by a membrane known as the veil. As the mush- 

 room develops this becomes detached from the circumference 

 of the cap and may either fall off or remain attached to the 

 stalk, when it is known as the ring. In some species, when 

 very young, the whole mushroom is inclosed in a membrane 

 called the volva; this is soon torn apart but traces of it may 

 remain even in the mature state as wart-like projections on 

 the cap or as a cup-like structure on the base of the stem, out 

 of which the stem grows as from a socket. This cup is a 

 mark of the highest importance in distinguishing the dan- 

 gerous varieties. Poisonous mushrooms may be divided into 

 two classes: those which are deadly and those which only 

 produce nausea or some other digestive disturbance, but are 

 not usually fatal. It is believed by authorities that all of 

 the deadly varieties show the cup in some form at the base of 

 the stem. If, therefore, one becomes familiar with its appear- 

 ance, and is able to detect it, he will be able to avoid the 

 chief dangers of poisoning. 



At least two of the deadly varieties are common in New 



