38 BOTANY AND PHARMACOGNOSY. 



and barberry. The teleutospores or " winter spores " (Fig. 24, 

 //), as they are called, because of their carrying the life of the 

 plant over the winter season, consist of two cells. These spores 

 persist on the leaves and stems of wheat over winter and in the 

 spring they germinate (Fig. 24, A). From each cell a myceHum 

 (promycelium or basidium) consisting of two to four cells arises 

 (Fig. 24, A, p), and from the tip of each branch of the promy- 

 celium a spore known as a sporidium develops (Fig. 24, A, s). 

 The sporidia are scattered by the wind and when they fall on 

 the barberry leaves (Fig. 24, B) they germinate, producing 

 a dense mass or mycelium which penetrates into the tissues 

 of the host. 



Sooner or later, just within the undersurface of the leaf, there 

 is formed a more or less spherical, dense mass, which grows out- 

 ward, breaking through the surface, forming a cup-like receptacle 

 known as an secidium (Fig. 24, C). The secidia or cluster cups, 

 are orange or yellow and are filled with perpendicular rows or 

 chains of spores which arise from the basidium-like mycelium 

 below. The spores, which have received the name .ecidiospores, 

 are somewhat spherical or polyhedral, and contain a reddish- 

 yellow oil. They are scattered by the wind and falling upon the 

 wheat plant (Fig. 24, E) germinate immediately, forming a dense 

 mycelium. At first it produces what is known as a " summer 

 spore," or uredospore (Fig. 24, G), giving rise to the reddish- 

 brown spots and stripes on the leaves and stallts of the wheat 

 plant. The uredospores are one-celled, and are carried by the 

 wind to other wheat plants, thus rapidly spreading the disease. 



The uredospores arise in much the same way as the teleuto- 

 spores (Fig. 24, H) which form brown patches later in the sea- 

 son, and which have been already considered. The teleutospores 

 last over winter on the old wheat plant, and in the spring begin 

 again the life cycle of the rust. The plant which results from the 

 germination of a teleutospore gives rise to sporidia which are 

 carried to the barberry leaves where jecidiospores are produced. 

 The latter are then carried to growing wheat, forming first uredo- 

 spores and later teleutospores. It should be remembered that 

 these are all asexual spores. In regions where there are no bar- 

 berry plants to act as host the secidiospore stage is omitted. 



