Pole Evans . — The Cereal Rusts. 
45 * 
In May, 1904, Klebahn ( 25 ) in ‘Bemerkungen liber das Mycel des 
Gelbrostes und liber die neueste Phase der Mycoplasma- Hypothese * tries to 
find an explanation for some of the phenomena represented in Eriksson 
and Tischler’s paper. 
In June, 1904, Eriksson ( 15 ) published a second paper on P. glumarum. 
entitled ‘ P uccinia glumarum (Schm.), Eriks, and Henn., in der heranwach- 
senden Gerstenpflanze \ the third of the series, ‘ Uber das vegetative Leben 
der Getreiderostpilze.’ 
But as this paper is solely concerned with what Eriksson still calls the 
mycoplasm stage of the Fungus, it does not concern us here, for we shall 
confine our attention for the present to the normal histology. 
In conjunction with Marshall Ward ( 34 ) I studied the histology of 
this rust in very great detail. It has been examined in a number of varieties 
of wheat, under various conditions of growth, normal as well as abnormal. 
Two varieties were used rather more extensively than the others for this 
purpose. 
3. The one known as 4 Red King ', because it was one of the most 
susceptible of the many varieties grown by Bififen at the University 
Experimental Farm. 
2 . The other was Michigan Bronze, the same variety as that with which 
Eriksson worked. This was chosen partly because it also is a very 
susceptible wheat to Yellow rust, and partly because it had been specially 
recommended by Eriksson. 
Histologically the most striking point of difference between the Uredo 
of P. glumarum and the other forms under discussion is that in P. glrnna- 
rum the hyphae are extremely thick, frequently measuring from 10-19// 
across, and at an early stage are seen to be crammed with nuclei ; whereas 
in the other forms the hyphae are only 3-5 // thick, and have but few nuclei 
arranged usually in single file. 
Germination of the Spore. 
The spore on germinating puts out a simple and very delicate germ- 
tube, which runs along the surface of the epidermis until it comes to a stoma, 
where the tip of the germ tube swells slightly and forms a fragile vesicle, 
the sub-stomatal vesicle, which applies itself closely to the inner face of 
the stoma. 
Into this large and thick-walled vesicle the whole contents of the spore 
are poured, and it is frequently seen crammed with nuclei only forty-eight 
hours after infection (PI. XL, Figs. 13, 14, and 15). 
This sub-stomatal vesicle is generally of a definite shape, being usually 
cylindrical with rounded ends. 
In diameter it measures from 8 to 19//. Its position relative to the 
stoma is also very definite, for it lays itself with its long axis parallel to 
