MAMMOTH CLOVER RUST 



251 



spore examinations and germinations, for imbedding and other 

 work. Aeciospores allowed to fall in a drop of tap water on a 

 glass slide, germinated 98 per cent in 24 hours. Some germ tubes 

 were 0.7 mm. long. Measurements of aeciospores mounted in water 

 were as follows: 16-26x16-28 microns. Standard 20x24 (thirty 



/W^ r^MOT-H Cloi/eh 



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Pig. 86. — Peridial cells drawn from a prepared slide. Outer walls averaged 

 4 microns, inner walls, 2 microns. The upper cell was the only one on which 

 striations were observed on the outer wall. 



measured). This would tend to show the aeciospores of red clover 

 rust are larger than those on mammoth clover. These spores are 

 shown in figures 84 and 85, also in figures 86 and 87. 



Uredin'wspores. — Urediniospores collected October 10,- 1918. ger- 

 minated by February 13, 1919, about 75 per cent. Those on the 

 stems seemed to retain their vitality longer than those on the leaves. 

 On February 20, 1919, but two of the spores on the leaves germi- 



