Sniitts in their Relation to Rusts. 



4t 



but these coiiidia are not di'tiiiite in nuinber and may be produced more than 

 once from the same cell. This multiplication of the conidia seems a necessary 

 consequence from the fact that there is only one kind of spore. The conidia 

 may cither directly germinate and produce the sporophyte, or they may 

 multiply in a yeast-like fashion before doing so, according to the supply of 

 nutriment. The yeast-like budding of the conidia not only multiplies the 

 means of reproduction, but carries the fungus over the period when no host- 

 plants are available. The germination of the teleutospore in both rusts and 

 smuts does not always result in the production of a promycelium. In the 

 rusts every gradation may be observed from the ordinary germ-tube as in 

 aecidiospores and uredospores to the special conidia-bearing promycelium. 

 Its mode of germination evidently depends largely on surrounding conditions. 

 Fischer^ observed this in Gymnosporangium, where conidia were oiily formed 

 in air, while in water an elongated germ-tube Avas produced, and Magnus ^ 

 has repeatedly observed that when the teleutospores of Puccinia graminis 

 were germinated in water, they produced a germ-tube just like that of a 

 uredospore. The teleutospore in the rusts has therefore departed from the 

 ordinary mode of germination of producing a germ-tube which directly 

 infects the host-plant, but multiplies itself by means of minute conidia suited 

 for aerial conditions, and giving rise in the host to a mycelium which bears 

 the sexual cells. The production of conidia, too, outside the host-plant 

 will also have an invigorating effect when they are nourished in a saprophytic 

 manner. Brefeld^ cultivated the conidia of rust fungi in a nutritive solution, 

 and found that they budded so as to form secondary and tertiary conidia, 

 and in smuts this mode of nutrition has produced the most luxuriant budding. 

 While in the smuts the spore produces generally a promycelium bearing 

 conidia, there is frequently only hyphae, and in infectioii through the flower 

 it is the rule for the spore to germinate direct and form a mycelium. 



If we compare the life history of a smut with that of a rust there is seen 

 to be partial resemblance, with important differences such as the absence of a 

 sexual stage. There is sufficient resemblance, however, to indicate some 

 affinity, and the question is as to the nature of it. 



As to the origin of the smuts, we can only arrive at a reasonable conclusion 

 by taking all the facts into consideration and comparing them with others, 

 seeking to find a place in the general scheme of life where they best fit in, and 

 associate them with those forms with Avhich they are most in agreement. 



Brefeld regards them as having been derived from the Phycomycetes, and 

 as this group possess both sexual and asexual forms of reproduction, they 

 are supposed to have originated from the latter. He also lays a great deal 

 of stress on the fact that the spore on germination produces what he considers 

 a basidium, and since the rusts also give rise to a similar structure, more 

 definite and more nearly approaching the type, he regards the smuts as the 

 preeoursors or progenitors of the rusts, and through them of the whole group 

 of Basidiomycetes. But, as we have already seen, there is room for difference 

 of opinion as to the origin of the Basidiomycetes, and consecjuently of the 

 relation of the snmts to them. 



My own idea is that the Ustilagineae may be simply regarded as forms 

 which have a distinct alternation of a saprophytic with a parasitic stage, 

 and with sexuality grafted on to this, they originated the TJredineae. It is 

 considered that the promycelium bearing conidia is a saprophyte, because it 

 generally grows freely in a nutritive solution 



It is now generally accepted that all fungi were originally saprophytes, 

 living upon dead or decaying vegetable matter, and that some of them 

 gradually became accustomed to a parasitic habit. The division of fungi 

 into saprophytes and parasites is convenient, but not natural, for there are 



