290 NINETEENTH REPORT. 



Other Species: 



Similar inoculation experiments were performed upon crimson clover 

 (T. incarnatum) , white clover (Z". repens), sweet clover (Melilotus alba), 

 alfalfa (Medicago sativa), pea (Pisum sativum), bean (Phaseolus vul- 

 garis), and vetch (Vicia villosa). These were uniformly without suc- 

 cess. Among the non-legumes the following plants were tested and 

 found to be not susceptible to the disease: Potato, tomato, cucumber, 

 muskmelon, cabbage, rape, and lettuce. So far as the experimentation 

 has been carried, the red clover is the only plant attacked by this parasite. 



THE HOST IN DISEASE. 



1. Morbid Anatomy : 



For a histological study of the diseased tissue, the material was 

 treated in the following manner: 

 Gilson's fixing fluid, 6-8 hrs. 



Washed in 70% alcohol until odor of acetic acid disappeared. 

 70% alcohol 24 hrs. 

 * From this point, dehydration, embedding, until the sections were 

 ready to stain, were proceeded with in the usual manner. 

 Staining: — Weak Delafield's haemotoxylon, 4-6 hrs.; wash in water 

 20-30 mill. Eosin, 30-45 sec. ; clear in phenol-turpentine ; mount 

 in balsam. 

 The fixing and subsequent treatment failed to remove the brown color 

 from either the dead tissues or the spores and conidiophores. Peroxide 

 of hydrogen likewise failed to bleach this color. By this staining process 

 the mycelium within the tissue was stained deep purple, the healthy 

 tissue, red to light purple, and the diseased tissue either a reddish brown 

 or not at all (retaining its original brown color). 



The diseased spots were only about one-third to one-half as thick as 

 the normal tissue. The cells composing the spot were almost completely 

 collajised. Within the spot proper the cells were almost entirely dis- 

 organized and permeated with the older mycelium. This mycelium is 

 brown in color, septate, branching, and of a more or less homogeneous 

 structure witliout any vacuoles. From both sides of the leaf, at irregular 

 intervals, spore bearing conidiophores project, their lengtli varying from 

 1-3 times that of the spore. ^ 



Near tlie edge of the spot the young mycelium may be seen spreading 

 intercellularly and to a certain extent intracellularly into the adjacent 

 healthy tissue. The mycelium does not as a rule at once emerge from 

 the leaf, but spreads laterally among the cells and may grow for a 

 considerable distance immediately underneath the epidermis. (PI. XIV, 



'This fixing fluid did not, as it is reputed, serve to retain the spores upon the conidio- 

 phores. 



