Winter Meeting. 353 



may be said to be about one two-hundredths of an inch; that it would 

 require about two hundred of them, laid side by side, to make an inch — 

 each one, therefore, is about equal in diameter to the cut-edge of good 

 book paper. Now, any of these plant cells may harbor scores of the 

 vegetable threads lying side by side of a fungus, or, as more often oc- 

 curs, one of these threads may push its way between two such cells 

 without causing sufficient separation to attract the attention of a micro- 

 scopist unless he is specially looking for this very thing. 



Besides their invisibility on account of size, these peculiar little 

 plants (for they are true plants, each after its kind) have very different 

 methods of growth and development from their larger, better-grown 

 and much higher ranked associates bearing green leaves. These fungi 

 have no leaves nor flowers. They do produce myriads of reproductive 

 bodies called spores, but these again are not seeds. When they ger- 

 minate no embryonic plantlet unfolds. There is no embryo in a spore. 

 It is simply a minute cell, one cell, whose wall or coat may push out at 

 one or more points into an elongate thread. This is germination, and 

 this thread may work its way into the substance of the green-leaved 

 plant on which it preys, where it becomes what is called the mycelium or 

 vegetable part of the fungus. Its business is now to absorb from the 

 tissues of the host plant the nourishment for its own growth. It is a 

 robber, and one without conscience. It not only helps itself to stored 

 fciod supplies,. but it carries ruthless destruction along with its thievery. 

 Besides robbery and the imposition of its intrusion, it poisons and cor- 

 rodes ; it is not only a thief, but an ungrateful destroyer as well. 



Having sucked the substance from the invaded tissues of the suf- 

 fering plant, the fungus prepared for its own reproduction by produc- 

 ing one to several kinds of spores. That is, certain of these parasites 

 only bear at any one time one form of spores ; others produce simultane- 

 ously or more often serially two, three or even four spore forms, each 

 perhaps suited to special conditions or circumstances. More often what 

 are called conidia are first formed during the earlier stage of the 

 parasite, usually before its vegetable growth (that of the threads or my- 

 celium) has ceased, and then during the period of ripening or maturity 

 the so-called asco-spores are^ developed. 



The conidia are borne on the free ends of more or less modified 

 mycelial threads. We may represent these conidia by sticking a small 

 apple on the point of a lead pencil and holding the latter erect— the apple 

 representing the spore and the pencil the fertile thread, now the spore- 

 stalk. There may be any number of these fruiting threads, from one to 

 thousands, arising from the same mycelium, which has, originated in the 



H— 23 



