Origin of Spore-forms. 35 



echinulation, and germ-pores, but still they are resting-spores with thick- 

 ened walls. Fischer 1 has also illustrated the transition in a series of two- 

 celled teleutospores of Gymno sporangium confusum, which have all ger- 

 minated, and which show a dense thick membrane at one end of the series 

 and an excessively fine one at the other. And Dietel 3 has pointed out 

 that the occurrence of thick and thin-walled spores in species of Gymno- 

 sporangium is quite common, and that it is a character of the genus that 

 the teleutospores formed in the interior of the gelatinous mass are thin- 

 walled, while the external ones are thick-walled. The gelatinous substance 

 is formed from the gelatinous walls of the stalks of the teleutospore, and 

 readily absorbs the rain-water and thus facilitates the germination of the 

 spore. Another important difference between the uredospore and teleuto- 

 spore of Uromyces is that while the latter only possesses one germ-pore, 

 the former has two or more often arranged as an equatorial band. But 

 here again Magnus shows in species such as U. proeminens (DC.) Pass, 

 and U. tuber culatus, Fckl., every transition from thq normal teleutospore 

 with apical germ-pore, through one with the germ-pore becoming somewhat 

 lateral, then with apical and lateral germ-pores, until the typical uredospore 

 is reached with a band of germ-pores confined to the equator, or several 

 scattered. 



In Puccinia podolepidis there is often a germ-pore on either side of the 

 upper cell of the teleutospore, as shown in PI. XXIX., Fig. 257. A third 

 and very important difference between the uredospore and teleutospore lies 

 in the mode of germination. Not only does the uredospore germinate im- 

 mediately on maturity, but it puts forth a germ-tube which penetrates 

 directly into the host-plant, while the teleutospore often undergoes a period 

 of rest and does not directly reproduce the fungus, but gives rise to a 

 piomycelium bearing promycelial spores, which germinate and enter a 

 host-plant. It would appear at first sight asf if this mode of germination 

 created a distinct barrier between the two kinds of spore, but when closely 

 looked into there is considerable variation in the germination of the teleuto- 

 spore, and under certain conditions it may forego the production of inter- 

 mediate spores. 



Kienitz-Gerloff 1 has shown that in Gym no sporangium clavariaeforme, 

 Jacq., the thin- walled teleutospores do not produce' a promycelium and 

 promycelial spores, but simply a germ-tube like that of a uredospore. And 

 Dietel 3 has further shown that both thick and thin-walled spores may 

 sometimes germinate in this way, and thus serve the purpose of the uredo- 

 spore occurring in other genera. Fischer 1 has also pointed out the influence 

 of external conditions on the mode of germination, the sporidiola, only being 

 formed in air, while in water or in the interior of the gelatinous mass 

 surrounding the spores, an elongated germ-tube is formed. This has been 

 corroborated by Blackman 1 , who found that the germ-tube is incapable of 

 sporidiola formation when submerged, and that under these conditions it 

 continues to grow in length until its reserve material is exhausted. He 

 also found that when germ-tubes of Phragmidium rubi were produced in 

 water, they might become divided into four cells, as if about to bear 

 sporidiola, but these cells, instead of following the ordinary course, rounded 

 themselves off and separated. Fischer observed in Gymno sporangium 

 confusum that the cells of the promycelium separated before forming sterig- 

 mata and promycelial spores, but Blackman, in a MS. note to his paper 1 , 

 kindly sent to me, says: "These are the cells of the promycelium which 

 are rounding themselves off and becoming directly sporidia." So that there 

 appears to be every gradation in the germination of the teleutospore. from 

 the production of a simple germ-tube to the division of the germ-tube into 

 cells which germinate, and finally the promycelium bearing promycelial 



