3 o8 



GENERAL MORPHOLOGY OF PLANTS 



Fig. 257. 



Spores of "bunt," or "stinking 

 smut" of wheat (Tilletia tritici) 

 germinating. A, spore producing 

 promycelium and young sporidia. 

 B later stage, sporidia mature and 

 conjugating in form of letter H. 

 C-D, germinating sporida forming 

 secondary spores. 



than the normal grains. 



into the shoot. It then continues to grow along with its host, as 

 in the case of the oat smut. Beside the loose smut of barley 

 there is another, the covered smut (U. hordei], so called because 



there is a thin membrane, the rem- 

 nant of the palets, which covers the 

 mass of smut, so tfyftt it does not so 

 readily scatter. There is also an- 

 other kind of wheali smut, the stink- 

 ing smut (two species), so called 

 because of its foul o(Jor. This smut 

 injures only the interior of the wheat 

 grain, which it changes to a greasy 

 mass of black smufspores covered 

 by the uninjured seed coats and ovary 

 wall. The grains have the appear- 

 ance externally of being perfectly 

 sound, but they are somewhat stouter 

 Infection takes place as in the case of 

 the oat smut, but the promycelium of the germinating spore is 

 undivided, and the sporidia, which are narrow, long, and slightly 

 curved, are borne in a cluster at its apex. 



459. Treatment for the prevention of smut. To prevent 

 the loose smuts of wheat and barley, seed should be selected from 

 fields free from smut. Oat smut and the stinking smut of wheat 

 can largely be prevented by treating the seed wheat with forma- 

 lin, or by a solution of copper sulphate, or by hot water (at 128- 

 132 F. for a few minutes). In the case of corn smut infected 

 stalks should be cut out and destroyed before the smut masses 

 ripen. 



Rust Fungi (Uredinales).* 



460. The rust fungi. There are a large number of species of 

 rust fungi on grasses, cereals, herbs, trees, and ferns. All of 

 them are parasites, and some cause great injury and loss. The 



* The wheat rust can be used for the practical study. If the cluster cup on 

 barberry cannot be had, use other cluster cups. 



