286 NINETEENTH REPORT. 



All diseased or otherwise weakened leaves were removed from the 

 plant. All were drenched with water and sprayed with a suspension of 

 spores. An effort was made to make the amount of spray as nearly as 

 possible proportional to the quantity of foliage in each group. 



From these infection experiments and the general observations through- 

 out the work, besides observation in the field, it seems likely that the very 

 young leaves are more susceptible to the attack of the fungus than are 

 the older leaves. This is perhaj^s due to the more tender and succulent 

 condition of the young leaves. As a corrolary of the leaf condition, we 

 find young plants more susceptible than old. For example, in West 

 Virginia, in 1905, the disease was reported as causing a great loss of 

 young clover. 



Stem and petiole infection: 



Although numerous infection experiments by spraying a suspension of 

 spores upon the plant were made, in no case was the infection of the 

 stems or petioles observed as the result of such a method of infection. 

 This may be due to the fact that a drop of spore-containing water adheres 

 with difficulty to these parts of the plant and may roll off before the 

 fungus has a chance to penetrate. Infection of the petioles, however, 

 was readily obtained by inoculating with a small mass of fungus growth 

 and then tieing cotton around the part inoculated. Within five to seven 

 days dark brown to black, linear streaks developed. Similar attempted 

 inoculations made upon the stems have not been successful. In anothfer 

 experiment, longitudinal slits about 1 cm. in length, were made upon four 

 old, woody stems, and the fungus inserted in the wound. Even after two 

 weeks there was no sign of infection. Some of the inoculum was removed 

 and examined: the spores had merely germinated but seemed to have been 

 incapable of proliferating the tissue of the stem. This may be due to 

 the comparative dryness of these older stems. 



Only in a few rare cases have infected petioles been seen in the field. 

 Young leaflets when inoculated by Method 2 may be eventually destroyed 

 and the fungus sjDread from them to the petiole. Petioles so infected 

 have a black, pinched appearance near the base of the leaflets (Plate 

 XIII, Fig. 9a). 



Floral and Seed Infection : 



Floral infections were undertaken with the idea of infecting the seed. 

 Reference to the statement of Milburn (1915) concerning the presence 

 of the fungus in the seed, has already been made. At various times 

 during the summer flower heads of red clover in early, full, and late 

 bloom respectively were inoculated by Method 1, but in no case was the 

 infection of any floral part of the seed obtained. Flowers from plants 



