MICROSCOPIC INVESTIGATION. 75 



of it as the " manna of the poor." In Transylvania the oyster-mush- 

 room is so abundant, and is so largely used, that tons of it may often be 

 seen in the markets; and in some parts of Germany the Morel-mush- 

 room is so popular, that the people, finding it to grow best on a soil 

 treated with wood-ashes, were accustomed to burn down portions of the 

 forests in order to secure favorable spots for its cultivation ; a i)ractico 

 which the government ultimately found it necessary to interdict. 



It is hoped that the collection of drawings, which has been made with 

 so much care, will serve to call i)ublic attention to the value of the mush- 

 room as an article of food, and at the same time furnish means of dis- 

 criminating between the poisonous and edible varieties of the plant. 



Particular pains have been taken to represent the last-named class of 

 plants as fully as possible, a number of collectors having been em- 

 ployed for the parpose in various parts of the United States. Among 

 these may be mentioned. Professor Peck, of New York, who, in that 

 State alone, gathered no less than eighty species of mushrooms, includ- 

 ing several which are new" to science. The specimens furnished by Pro- 

 fessor Peck are admirably copied, and colored to nature. There are also 

 several excellent photographs made from specimens furnished by various 

 collectors, representing different genera and species of the same class of 

 plants. 



Another series of drawings illustrates the action of pear-tree blight, 

 showing the effects of the chemical changes which take place in the 

 interior structure of the tree under the attacks of the fungus to which 

 this disease is due. The disease of plum and cherry trees, known as 

 "black-knot," is illustrated in a similar manner, some of the drawings 

 exhibiting it as it appears to the naked eye, while others show in detail 

 its distorted, woody structure. The fungus which produces it is also 

 shown at various stages of its growth. 



The fungus Feronospora infestans, which causes potato-rot, is illustrated 

 in the various stages of its growth. There is also a series of drawings 

 of its "resting-spores," recently discovered by Prof. Worthington Smith, 

 and so named from the fact that they remain for months in a stationary 

 condition, or, in other words, rest for that time without germinating. 



There is an interesting series of drawings, representing, as seen 

 through the microscope, the mold of bread, cheese, jellies, &c., and illus- 

 trating their habits of growth, a knowledge of which may often be 

 useful in preventing beer or milk from souring and wine or bread from 

 becoming " ropy." 



One of the most curious of the cryptogamic plants is the Protococcus 

 nivalis, which, we believe, was first found by Captain Parry, during his 

 northern exploration, and to which was given the name of "red snow," 

 from the fact that it gives its own red color to the surface of the snow 

 on which it grows. This singular little plant is represented by several 

 drawings of exquisite finish and color. 



The fibers of hemp, flax, jute, ramie, esparto-grass, and Australia,n 

 flax, as well as wool, silk, calf's-hair, and the liair of the Cashmere and 

 Angora goats, are exhibited as seen through the microscojie, both in 

 their natural condition and under various forms of chemical action. In 

 the course of my investigations on this subject, I found a number of 

 new chemical tests by which the presence or absence of certain of these 

 fibers in every fabric may be determined. This series of drawings will, 

 therefore, be of considerable interest to manufacturers of textile fabrics, 

 to dealers in that class of goods, and to the Government, which, besides 

 being an extensive purchaser of clothing for the Array and Navy, is 



