11 



the Surgeon-General's library at Washington. Some assistance has 

 also been obtained from the recent special publications of Dr. H. H. 

 Rusby and Prof. Byron D. Halsted. The figures, with the exception 

 of Nos. 2, 18, and 21, were drawn by Mr. F. A. Walpole, the artist of 

 the Division of Botany. 



GILL FUNGI (AGARICACEAE). 



DEADLY AMANITAS. 

 Amanita. 



The amanitas belong to the class of plants known as gill fungi 

 (Agaricaceae), and include most of the plants popularly called toad- 

 stools and mushrooms. Many of these are delicious articles of food, 

 and they are rapidly becoming more and more used for this purpose in 

 the United States. In appearance noue are more attractive than the 

 deadly amauitas, especially the two which are treated of in this bulle- 

 tin. A few of the 25 or 30 species of this genus are edible, but as fully 

 one-third are known to contain deadly poisons, and as this is not so 

 generally true of any other group, it is important that its characteris- 

 tics should be pointed out. 



The amanitas form the most typical genus of that group of fleshy 

 fungi which is characterized by vertical radiating plates or gills on the 

 under surface of the cap. In the early stages of growth the amanitas 

 are egg-shaped and are entirely enveloped by a white flocculent cover- 

 ing, which is ruptured as the stem lengthens. In a few species this 

 covering adheres in loose, corky patches^ to the top of the cap, as seen 

 in fig. 1, but sometimes it slips away from the cap entirely and forms a 

 more or less continuous sheathing cup at the base of the stem at the 

 point of enlargement, as shown in fig. 2. This flocculent covering and 

 the invariably bulbous base of the stem are the most important charac- 

 teristics of the genus, while the different position of the flocculent cov- 

 ering after rupture helps to distinguish the species. These features 

 are well pronounced as a rule, but sometimes it requires some searching 

 to find the cup. 



Besides the general envelope there is also a secondary one which at 

 first covers the gills, extending from the stem outward in all directions 

 horizontally to the rim of the cap. This breaks away from the cap 

 before maturity and forms a more or less perfect and conspicuous col- 

 lar about the upper part of the stem. Except in the case of one species 

 noted below, the gills and spores are white. The geographical distri- 

 bution of these fungi is not well known, as comparatively few individu- 

 als have studied them carefully. 



