SIMPLE PLANTS 209 



posed 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 spor- 

 angiophores ( ), 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 hphae 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 re- 

 sulting 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, 

 but 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. This means that molds are a degen- 

 erate 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 



Some of the difficulties of classification may be observed here by 

 noting that 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, born on little club-shaped hyphae, or 

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

 pathogenic fungi bear many names and cannot be accurately placed, be- 

 cause pathologists use other than the regular botanical terms and mean- 

 ings, as shown by the table below. 



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. 



