UREDINALES 575 



a dicaryon migrates, occasionally branches and cuts off at the ends a 

 series of thin- walled teliospores which are at once capable of germination. 

 Furthermore in floras two other genera are included, Endophyllum 

 and Kunkelia, whose aeciospores, as mentioned earlier, occasionally 

 germinate with a basidium, as do teliospores. As the descriptive sys- 

 tematise on practical grounds, regards the germination of the spores as 

 decisive, he designates these structures as teliospores, while the compara- 

 tive morphologist must consider them as aeciospores because of their 

 ontogeny. 



Pucciniaceae. — Here appears an entirely new phenomenon: the 

 teliospores are stipitate as the urediniospores, and they arise as daughter 

 cells of one mother cell which divides into the teliospore and the stipe 

 cell. The binucleate hyphae push forward from the interior of the host 

 toward a definite point of the epidermis, join together to a loose stroma, 

 swell terminally and change their end cell to a basal cell. Only in 

 Gymnosporangium, the subterminal cells function as basal cells and the 

 terminal cells degenerate and become buffer cells (B. O. Dodge, 1918, 

 1922). By lateral growth the basal cells are able to repeat the formation 

 of initial cells, just as in the uredinia (Fig. 388, 5). At maturity, the 

 epidermis is ruptured by the pressure of the whole telium and individual 

 spores lie free. In contrast to the urediniospores, they usually remain 

 closely adherent to their stipes and germinate in situ. Before germina- 

 tion, the dicaryon fuses to a diploid nucleus: the teliospores here play 

 the role of zeugites. 



In the simplest cases, as in the Asiatic Blastospora, in the West Indian 

 Botryorhiza and in the cosmopolitan heterogeneous Uromyces, they 

 consist of a single cell whose wall, in Blastospora (Fig. 389, 1) and Botry- 

 orhiza (Fig. 387, 1), is hyaline and thin, and in Uromyces (Fig. 387, 2) is 

 usually brown and thick, bearing a curious, apical, germ pore. In 

 Blastospora, they germinate without a rest period; in Uromyces, they are 

 generally true resting spores. 



In the following genera, the apical daughter cell destined for a spore, 

 before the thickening of its wall and the fusion of the dicaryon divides by 

 septa into two or more chambers each of which, at germination, produces 

 a basidium. 



In Puccinia (Fig. 387, 3) there are two chambers, of which the upper 

 possesses an apical germ pore, the lower a lateral one. In certain species, 

 however, the formation of the septum may be entirely absent, so that 

 many spores, in some cases even a majority, in the telium remain uni- 

 cellular. As, however, the two-celled spore form is considered the higher 

 for purposes of classification, the species must be placed in Puccinia; and 

 then the spores which have remained unicellular are called mesospores. 

 In certain other species, there are at times produced two habitually 

 different spore forms; thus Puccinia Veronicarum, in spring and summer, 



