686 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM 



Teleutospores (from reXeuT?}, 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 abstrieted. Commonly the teleutospores are in 

 rows 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 JScidio- 

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

 closed. Both uredospores and secidiospores differ 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. 678), 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 Uredinese 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. primulce); others possess teleutospores only 

 or teleutospores and one of the other types, whilst in others again all the forms are 

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

 of developing the diiferent stages on two host-plants (known as heteroecism) is 

 by no means uncommon amongst the Uredinese. 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 secidiospores on Pinus sylvestris (the latter stage 

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

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

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

 juniperinum, which produces its teleutospores on the Juniper, its ^cidiospores on 

 the Mountain Ash (Pyrus aucuparia). These three may serve as types of a very 

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

 famous of all. The secidium-stage (accompanied by pycnidia) arises in spring on 

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

 on the same host, but only on Wheat, Oats, Eye, 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 which conidia 

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

 and from the mycelium which arises from them fresh secidium-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 Barberry bushes is an obvious measure. In 



