170 THE AMERICAN MONTHLY [August, 



cismal Pucciniae. Because of their complete development, however, 

 the general characteristics will be found to be closely common to those 

 of the whole order. 



Biology and Classification. — The Uredineaa comprise an order of 

 parasitic fungi which infest the living tissues of the higher plants, being 

 with few exceptions confined to the phanerogams, attacking the most 

 succulent parts. All the species are highly parasitic, each growing 

 upon host plants specially suited to its particular development, without 

 which providers of nourishment they cannot exist. Wherever flowering 

 plants are found some forms of the uredines may be found associated 

 with them, the fruit forming definite spots upon the host, the parasite 

 living upon but not destroying the underlying tissues. In this particu- 

 lar these fungi show their high position in the scale of parasitism. Un- 

 like the lower parasites, the semi-saprophytes, such as Cladosporium, 

 which may live upon the decaying substratum, the death of the parasite 

 invariably follows that of the host tissues. 



The plant body is composed of a variously branching, interlacing, and 

 coalescing network of hyphae, ramifying and often fusing with the tis- 

 sues of the supporting plant. The vegetative hyphae possess essen- 

 tially the same form throughout all the different genera, but in the for- 

 mation of the fruit the plants display a wide range of polymorphism, 

 producing in certain species as many as four spore forms, in appearance 

 and surroundings apparently wholly distinct. 



The sexuality of the fungi has been a study pursued with much dili- 

 gence by mycologists, and in their attempt at the determination of rela- 

 tionships the yEcidiomycet.es have in no manner been slighted. Yet, 

 though De Bary * directed attention to the subject in regard to this or- 

 der over thirty-five years ago, no one has successfully demonstrated the 

 presence of a sexual process in the formation of any of the spore forms. 

 But the weight of argument seems to be with De Bary in considering 

 the ascidium the homologue of the sporocarp of the other Ascomycetes ;t 

 and Geo. Massee,| of England, affirms that in the case of yEcidium 

 ranunculacearum he has actually witnessed the development of an 

 oogonium and antheridium which immediately precedes the develop- 

 ment of the aecidium. 



The production of exceedingly dissimilar spore forms under widely 

 varying and unexpected conditions, the numerous inexplicable anoma- 

 lies connected with the development of the individual species, such as 

 the ability to perpetuate the species by means of only one spore form, 

 as in the Leptopucciniae, and the apparent absence of any sexual pro- 

 cess, have given rise to complications which may in a manner explain 

 our present meager knowledge of the proper relationship of the order. 



The accompanying phylogenetic diagram, as condensed from De 

 Bary by Ward,§ is given here as representing the most probable situa- 

 tion of the order in relation to the other fungi as fixed by our present 

 knowledge : 



* Die Brandpilze, 1853. 



t Morphology and Biology of Fungi, sec. Ixxix. 



j Annals of Botany, vol. ii, p. 47. 



§" On Sexuality of the Fungi," Quart. Jour. Mic. Sci., new series, vol. xxiv, p. 294. 



