210 General Biology 



that enzymes are produced in the hyphae which can make the bread or 

 fruit utilizable to the plant. 



Reproduction takes place by a number of upright stalks, called 

 sporangiophores ( ), growing from the mycelium. 



There is formed a spore-case, or sporangium, at the very tip of the stalk. 

 In this the spores are formed and, when the spore-case bursts, the dust- 

 like particles, which are really spores, are scattered about by air currents. 



There may be sexual reproduction in the molds quite similar to that 

 in Spirogyra. Two hyphae unite by their free ends and a wall forms, 

 thus producing two end cells which eventually become a single spore 

 with a very dark heavy wall. Here again, the gametes being similar, 

 the resulting body is a zygospore. The sexual process does not occur 

 very often. 



It is to be remembered that molds are plants. But growing as they 

 do in the dark, they have no chlorophyl and do not make their own food. 

 They feed on food already prepared, not on ordinary plant or animal food 

 as does man, for example, but on decaying matter or on food that has 

 already been digested by the host, either before or after assimilation. 



The so-called water-mold is both parasitic and saprophytic as it can 

 thrive either on dead or living fish. Molds are said to be a degenerate 

 form of green plants which have acquired a habit of making some other 

 organism do their work for them, rather than build their own food by 

 photosynthesis as plants usually do. 



PATHOGENIC FUNGI 



There are many difficulties in the way of working out a satisfactory 

 classification of the pathogenic fungi because botanists and pathologists 

 do not always use the same name or employ the same method. Botanists 

 classify fungi or mycetes ( ) as follows : 



1. Phycomycetes : algae-like fungi. (Fig. 99.) 



2. Ascomycetes: sac-fungi (asci) ; asexual spores formed in sacs. 

 (Fig. 100.) 



3. Basidiomycetes : spores, borne on little club-shaped hyphae, or 

 basidia. (Fig. 101.) (Includes smuts, rusts, and mushrooms.) 



Pathologists take the following points into consideration and 

 arrange their classification under the title of pathogenic protophytes : 



Most infectious diseases due to vegetable parasites are caused by 

 bacteria, but a few owe their origin to micro-organisms of a higher type, 

 namely, to the yeasts and molds. Two of the infectious processes caused 

 by yeasts, although comparatively rare, deserve brief consideration. 

 Both the organisms and the lesions they produce, microscopically and in 

 gross, resemble each other more or less closely. For this reason they 

 were for a long time confused with each other, but the differential char- 

 acteristics are now fairly generally recognized. 



