6S6 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM 



Teleutospores (fi'om reXcimj, an end), which are the type most universally present, arise 

 towards the end of the vegetative period. In the majority of cases they remain 

 dormant during the winter. On germinating they form a 4-celled basidium, from 

 each cell of which a conidium is abstricted. Commonly the teleutospores are in 

 i-ows of two, i.e. constitute spindle-shaped, 2-celled bodies, each cell (spore) of which 

 can produce a basidium. Sometimes the teleutospores are in many-celled rows, 

 occasionally solitary. The Uredospores (from uro, to burn) as a rule precede the 

 teleutospores and germinate at once. They are oval and unicellular. The yEcidio- 

 spores arise iu chains in special receptacles (the ascidium-fruits) which are at first 

 closed. Both uredospores and ajcidiospores difTer from teleutospores in that they 

 produce a mycelium at once on germination. They never form basidia and conidia. 

 A fourth sort of reproductive organ, a secondary conidial stage, is often found 

 associated with the secidium stage; this is the pycnidium (c/. p. 67S), a hollow 

 receptacle whose lining cells abstract tiny condia. The fate of these pycno-conidia 

 and the part they play in the life-history of the Fungus is unknown. 



There is thus in the Uredinere great variety in the kinds of reproductive cells. 

 Some species possess all of them and produce them one after another upon the same 

 host-plant (e.g. Puccinia galii and P. j)i'i'm.idce); others possess teleutospores only 

 or teleutospores and one of the other types, whilst in others again all the foi-ms are 

 present, but they are not developed upon the same host-plant. This latter property 

 of developing the different stages on two host-plants (known as hetervecisvi) is 

 by no means uncommon amongst the Uredineae. It is remarkable enough to merit 

 a short description here, though, of course, any exhaustive account of the family as 

 a whole is impossible. The following are well-known cases of heteroecism. Coleo- 

 sporiuin senecionis, which produces its uredospores and teleutospores on the 

 Groundsel (Senecio vulgaris), its eecidiospores on Pinios sylvestris (the latter stage 

 formerly known as Peridermiuvi pini); Puccinia graTninis, which produces its 

 uredospores and teleutospores on Wheat and other grasses, its aacidiospores on the 

 Barberry (this stage formerly known as jEcidium berberidis); Gymnosporangium 

 juniperinum, which produces its teleutospores on the Juniper, its secidiospores on 

 the Mountain Ash {Pyrus aucuparia). These three may serve as types of a verj- 

 large number of similar forms. Puccinia graTninis, the Rust of Wheat, is the most 

 famous of all. The fficidium-stage (accompanied hy pycnidia) arises in spring on 

 the foliage of the Barberry and the aecidiospores here produced cannot germinate 

 on the same host, but only on Wheat, Oats, Rye, or some other Grass. Here a new 

 mycelium is established bearing first uredospores and later on teleutospores. The 

 uredospores can germinate at once on other grasses, but the teleutospores remain 

 dormant through the winter, and in spring give rise to basidia from wliich conidia 

 are abstricted; these conidia can germinate only on the Barberry — not on grasses — 

 and from the mycelium which arises from them fresh scidium-fruits are developed. 

 In the absence of either host-plant (i.e. of the Barberry or of suitable Grasses) the 

 life cycle of the Puccinia is of course interrupted. For the extermination of the 

 Rust disease of cereals the removal of Barberrv bushes is an obvious measure. In 



