Z CIRCULAR 14 3, U. S. DEPARTMENT OF AGRICULTURE 



FUNGI IN GENERAL 



The plants known as fungi comprise a very large group and exhibit 

 great variation in form, size, color, and habit. The one important 

 character common to all fungi is the absence of the green coloring 

 matter known as chlorophyll, by means of which, through the aid 

 of sunshine, higher plants are able to manufacture their own food. 

 The structure of fungi is very simple; that is, it has not become 

 highly differentiated or specialized as in flowering plants. Fungi 

 have very simple physiological processes and are incapable of manu- 

 facturing their own food, but live as parasites or saprophytes, appro- 

 priating food already prepared by higher forms of plants. Occur- 

 ring as parasites, they are responsible for extensive losses to agricul- 

 tural crops and produce blights, rots, unsightly growths, rusts and 

 smuts of grain, and diseases of ornamental and forest trees. In- 

 juries from fungi are not confined entirely to plants but are some- 

 times the cause of disease in man and in animals. 



One of the great advantages pertaining to the study of fungi as 

 a hobby or diversion is that their occurrence, unlike that of many 

 other plants, is not limited to a short calendar period but extends 

 practically throughout the entire year. The appearance and abun- 

 dance of mushrooms are subject to great variation, largely depend- 

 ing on weather conditions. This variation is influenced not only 

 by the weather of the current season but also by that of the preced- 

 ing year. Two important factors in the growth of fungi are heat 

 and moisture. If the preceding year has been excessively dry, the 

 underground or vegetative part of the fungus, known as the myce- 

 lium, and the minute reproductive bodies, known as spores, may 

 have dried up or at least suffered a loss of vitality that would retard 

 or discourage the appearance of many fungi the following season. 

 On the contrary, a hot but wet season is highly conducive to the 

 abundant production of mushrooms. The almost phenomenal ap- 

 pearance of fungous growths under such conditions has led to the 

 stories of the seemingly miraculous appearance of mushrooms over- 

 night. That fungi develop very rapidly is partly explained by the 

 fact that much of the tissue is formed before the fungus breaks 

 through the surface of the soil. In addition, fungous tissue is espe- 

 cially adapted to the rapid absorption of water, and as a result the 

 growing plant expands very rapidly. 



As already mentioned, fungi exhibit a remarkable diversity in size, 

 form, and color. They vary from microscopic organisms, many of 

 which cause plant diseases, to the large woody growths present on 

 many injured or dying forest trees. In form or structure they range 

 from very simple 1-celled structures to the fantastic complicated 

 stinkhorn fungi. (Fig. 45.) The greatest variation in color may 

 also be observed. In some species the colors are often very unob- 

 trusive and quiet, while in other species they are striking in their 

 diversity and brilliancy. 



One very striking phenomenon exhibited by certain fungi is lumi- 

 nosity or phosphorescence. This character, while confined to a com- 

 paratively few fungi, is so striking or ghostlike as to have furnished 

 material for fairy stories and among the natives of certain countries 

 the basis for many superstitions. An Australian species is recorded 



