524 RESEARCHES ON FUNGI 



In the Uredineae, a basidium does not arise directly from one 

 of the hyphae which are to be found under the epidermis of the 

 host-plant but indirectly, through the intermediary of a special 

 body known as a teleutospore. A teleutospore is not an organ of 

 dissemination like the aecidiospore, the uredospore, and the basidio- 

 spore ; but, as van Tieghem has pointed out, it is a probasidium, 

 a cellular structure which is destined not to produce a new fungus 

 plant, but simply one or more basidia with the corresponding 

 basidiospores. A teleutospore is not set free from its place of origin 

 and therefore cannot be a factor in causing the dispersal of the 

 fungus species in nature : it germinates in situ, whilst still attached 

 to the tissues of its host.^ A teleutospore is essentially a resting 

 structure, i.e. a structure that can rest for a long period, especially 

 through times of drought and cold, without injury ; so that, sub- 

 sequently, when subjected to suitable conditions of temperature 

 and moisture, it can revive and germinate. Many teleutospores, 

 although able to rest without development for a long period, can, 

 under favourable conditions, germinate at once, as in Puccinia 

 Malvacearum. Other teleutospores, on the contrary, require a period 

 of rest, generally the winter season, before they can germinate, as 

 in Puccinia graminis. Usually teleutospores possess thick walls 

 which contrast with the thin walls of the non-resting uredospores 

 and basidiospores and which seem to be protective structures. 

 Moreover teleutospores, at any rate in many Uredineae, can be- 

 come quite independent of the cells from which they have arisen, 

 except in the matter of attachment, and also independent of each 

 other. Thus, for example, in Puccinia graminis, although in 

 nature, in order to secure the successful dispersion of the basidio- 

 spores, the teleutospores which produce them must remain attached 

 to the hyphae of the sorus on the host-plant, yet the teleutospores, 

 if artificially torn from their natural positions, isolated, and placed 

 under favourable conditions, will nevertheless germinate.^ 



^ This rule applies to the great majority of the Uredineae. but is not quite of 

 universal application, as there are a few exceptions to it. The exceptions Avill be 

 discussed in the next Chapter. 



- It must be admitted, however, that such germination is often abnormal, but 

 this is owing to the difficulty of securing the right conditions of moisture in small 

 closed chambers, etc. 



