FUNGI. — UREDINEAE. 



127 



soon ceases to grow, but forms instead on short slender branches smaller propagalive 

 cells, termed sporidia, which fall under the general conception of a gonidium as it has 

 been defined above. The germinating filament which produces the sporidia is a 

 promycelium. The sporidia in their turn put forth germ-tubes, which penetrate 

 through the epidermis-cells into the tissue of a host, and there give rise to a 

 mycelium which subsequently produces aecidia. In this case, which is represented 

 by Endophylliini Sempervivi, there is a single alternation of generations, in which the 

 alternating generations are the mycelium and the fructification (aecidium), with theslight 

 variation that the spores produce the mycelium with the intervention of a promyceHum 

 and its sporidia. The other extreme occurs in Aecidhwi Berbcridis {Puccinia 

 graminis), Aecidium Leguminosarum {Uj-omyces appendiculatus), and others, where new 

 mycelia are produced directly from the aecidiospores without the intervention of a 

 promycelium ; but these mycelia do not produce aecidia, but roundish gonidia 

 on crowded cushion-like basidia ; and by means of these gonidia, which are known 

 as iircdospores and can germinate at once, the mycelium is repeatedly reproduced 

 during the period of vegetation ; at a later period propagative cells of another kind, 

 the teleutospores, make their appearance in the generations termed the uredo 

 generations, and these do not germinate till the following year, when they produce 

 promycelia, from the sporidia of which arise the mycelia which bear the aecidium. 



A comparison of the second case with the first shows that in the former between 

 the production of the aecidiospores and of the promycelium certain generations have 

 been interposed, in which the organs of propagation (gonidia) are termed urcdo- 

 spores and teleutospores. 



Even in these well-known forms of the Uredineae a sexual act has not yet been 

 observed, but its existence must be considered as highly probable after what is now 

 known of the origin of the apothecia of the Lichens ; moreover spenjiatia are found in 

 the Uredineae formed in special receptacles, the spermogonia, and they usually appear 

 before the aecidia ; it is highly probable that the spermatia, here as in the Lichens, 

 perform the part of male organs, and if so the aecidia, the most complex product of 

 the development, must be considered to be sexually produced. Then the aecidium 

 will answer to the apothecium of the Lichens, or to the peritheciutn of the other 

 Ascomycetes, the aecidiospores to the ascospores, and the uredospores and teleuto- 

 spores will be, as has been said,' different forms of gonidia. Experience has shown 

 that the genera are most suitably named after the forms which bear teleutospores, 

 from which the genera Puccinia, Uromyces, Coleosporium, Melampsora and others are 

 already designated. 



The gonidial forms known as uredospores and teleutospores are not found in all 

 the genera of the Uredineae ; both are wanting, as has been stated, in EtidophyUion ; 

 the uredospores are absent in Roestdia ; both occur in Puccinia graminis, P. scssi/is. 

 and others. 



In many species the development is but imperfectly known, some of its stages 

 being as yet undiscovered ; but there are some in which the process is in fact 

 simplified. There are for instance genera in which only teleutospores are known, but 

 which reproduce themselves to an unlimited extent by their means without the 

 appearance of an aecidium; such are Puccinia Malvaccaruni and P. Dianlhi, 

 Chrysomyxa Abietis, and others. The layer of spores in C/irysomyxa bursts through 



