CHA P TER V.— COM PA RAT IV E REV IE W. — UREDINEA E. 2 8 1 



in the same way as the uredospores, only there are no intervening cells (Figs. 129, 

 130); but in Triphragmium three spores are formed on the same plane by simul- 

 taneous (?) division in the solitary acrogenetic mother-cell, and in Melampsora the 

 mother-cell is divided by longitudinal walls into several (four) spores placed side by 

 side. The teleutospores are generally distinguished from the uredospores by two 

 peculiarities as well as by their mode of germination. In the first place they do not 

 separate from the sterigma, but in most species remain with it at their place of origin 

 until they germinate; more rarely, as in some species of Uromyces and Puccinia 

 (Uromyces Phaseolorum, Puccinia fusca, and some others), they become disengaged, 

 though not from the sterigma, since they carry with them a portion of the sterigma, which 

 is severed from the hymenium by a transverse rupture. Secondly, all teleutospores are 

 filled when they are mature with a finely granular protoplasm which is either 

 colourless or coloured by a very finely comminuted reddish yellow fatty matter 

 surrounding a comparatively small spherical cavity, the cavity itself being filled 

 with a weakly refringent substance. Whether this is a nucleus or a space containing 

 a nucleus or something of another kind is not yet certainly ascertained. In other 

 respects, such as their special mode of formation, their connection with each other 

 and with the hymenium, their configuration and the structure of their walls, there is 

 considerable variety among the teleutospores, and the distribution of the Uredineae 

 into genera has been founded chiefly on these differences. The mode of germination 

 is very similar in them all; Coleosporium only differs from other genera in the 

 circumstance that the teleutospores, which are placed one above the other in rows, 

 generally four together, each put out one sterigma only in germination, and the 

 sterigma abscises a sporidium, so that a row of germinating spores resembles in 

 outward appearance the promycelium of other genera. 



It appears from the foregoing review that the simplest known course of development 

 among the Uredineae which form aecidia is found in the Endophylleae. But even here 

 between the aecidiospore and the next generation which forms aecidia there is always 

 an intervening alternating generation which forms gonidia, the promycelium with its 

 sporidia, though it is only a transitory state. In the two known species, Endophyllum 

 Sempervivi and E. Euphorbiae, a year elapses between the formation of two successive 

 aecidium-generations, and this time is employed in the complete development of the 

 mycelium in the tissue of the perennial host. There may possibly be species in which 

 the course of development is still further simplified by the absence of sporidia, the 

 germ-tube from the aecidiospore developing directly into the mycelium with aecidia ; 

 but these the simplest conceivable species are not known. The simple tubes which 

 may develope from the spores of Endophyllum when they are placed under water 

 do not become promycelia, and are, as far at least as we at present know, incapable 

 of further development. 



The intercalation of teleutogonidia and uredogonidia in the course of development in 

 the other species, either as necessary or at least as regular members of it, makes it more 

 complicated, and there are various degrees of complication in different species according 

 to the greater or less abundance or the entire absence of the uredo. Besides 

 these purely morphological gradations there are biological differences also, which give 

 an extraordinary variety to the actual living forms in the plants by frequent change of 

 combinations from species to species. The chief difference here is that the teuleuto- 

 spores of some species germinate as soon as they are ripe, those of others are obliged to 

 pass through a period of rest ; the former mature in the period of vegetation, the 

 latter mature at the end of one period and germinate at the beginning of the next. 



