— 133 — 



scend the petioles to reappear in other leaves previously unaffected 

 and there develop its spores ; also, that the spore forms which 

 appear in the spring do not arise from mycelium which has lived 

 over winter in the roots of the host. 



REPRODUCTIVE ORGANS. 



/. The Aecidium. — This form is not so abundant as the other 



two and does less injury. It is found upon 

 the White Clover, of which it attacks the 

 leaves and petioles, causing the latter to be- 

 come swollen and distorted. (Fig. 3.) When 

 it begins to develop, swollen and light-col- 

 ored areas appear ; later, are produced the 

 aecidia or ' ' cluster cups ' ' which appear to the 

 naked eye as minute, orange-colored spots. 



Each aecidium (Fig. 4) is a colorless, cup- 

 like body filled with chain-like rows of or- 

 ange-colored spores (14 to 22 fx in diam.*), 

 borne on the ends of erect hyphae which, as 

 well as the cup itself arise from the mycelium 

 within the leaf. 



Fig. 3— Leaf of Whit e Among these ' ' cluster cups, ' ' or developing 

 Clover with aecidia. before them, also more than once detected 

 during the winter, were found small- 

 er, nearty spherical bodies, the sper- 

 mogonia which appear as minute 

 brownish spots. Within each sper- 

 mogonium are produced delicate, 

 yeast-like bodies whose office is un- 

 known. 



II. The Uredo Form. — This ap- 

 pears as circular or elongated, 

 chestnut-brown spots or ' ' sori . ' ' 

 (Figs. 1, 2 and 5.) These are often so 

 abundant as to almost entirely cover 



the surface of the leaf, causing it , _ . , 



' I<iG. 4 — Two cluster cups or aecidia 



to wither and die. Each sorus ^th contained spores {* about 



consists of reddish -brown spores 50 diam.); also three acidio- 

 (14-21x21-25 fx) borne singly upon spores (X about 450 diam.) 



,^Srl 



* 1 ju = j^jjg millimeter = nearly -',,,,, of an inch. 



