36 



BULLETIISr 395, U. S. DEPARTMENT OF AGRICULTURE. 



and placed in dry cloth-covered jelly glasises (a) in the laboratory, where the tempera- 

 ture ranged from 18° to 25^ C, and (b) in the pathological garden in a covered, latticed 

 compartment of the type commonly used for housing meteorological instruments. The 

 cultures rapidly became air dry. The conditions precluded the further growth or 

 sporulation of the fungus. Germination tests were made at intervals. The results, 

 which are summarized in Table VII, show that in each series a considerable percent- 

 age of spores remained viable for more than three months. Had the spores been ex- 

 posed to wetting, however, it must be remembered that they would have germinated 

 with the advent of favorable conditions. Thus, it is not to be expected that conidia 

 ordinarily retain their viability for long periods. 



Table VII. — Summarized results of a longevity test of conidia of Cladosporium car- 

 pophilum frovi cultures, Madison, Wis., April 16 to October 25, 1915. 



Serial No. 



Date of test. 



Place of storage of 

 culture. 



Estimated germi- 

 nation in 3 days 

 (percent). 



Sterile 

 distilled 

 water. 



1 per cent 



prune 

 decoction. 



786 



Apr. 16, 1915 



do 



Laboratory 



Garden 



99 

 99 

 50 

 60 

 15 

 10 

 



99 



787 



99 



864 



Junes, 1915 



do 



Laboratory 



90 



862. 



90 



996 



July 23, 1915 



..do 



Laboratory 



Garden. . . 



90 



994 



90 



1004 



Oct. 25, 1915 



Laboratory 











DISSEMINATION OF CONIDIA. 



Studies planned to give insight into (1) the conditions under which 

 conidia of Cladosporium carpopTiilum are detached from the parent 

 fungus and (2) the more important methods by which thej^ are dis- 

 seminated are briefly outhned as follows: 



EXPERIMENTAL WORK. 



Experiment 1. — Colonies of the fungus were grown in tubes on steamed bean pods 

 over a bean decoction in such position that spores which might be abstricted or ab- 

 jected would fall into the liquid below and germinate. The experiment was run in 

 quadruplicate and continued for six weeks. The colonies developed vigorously and 

 sporulated profusely, but the decoction below remained sterile. After six weeks one 

 of the cultures was shaken so that the liquid came in contact with the colony. Within 

 three days the decoction was conspicuously clouded and darkened by the develop- 

 ment from myriads of spores which had been detached. 



This experiment was repeated with like results, while similar tests were made with a 

 variety of other media. The results were uniformly confirmatory. 



Experiment 2. — On April 19, 1915, severely infected peach twigs were placed in 

 moist cnambers. On April 23 a number of these twigs bearing abundantly sporu- 

 lating lesions were placed (a) in moist chambers and (6) in dry chambers 1 cm. above 

 glass slides smeared mth glycerin. These slides were examined microscopically at 

 intervals for two days. No spores were found. 



Experimeyit 3. — Sections of lesions were placed under the low power of the micro- 

 scope in such position that tufts of spores could be observed. Currents of air were 

 passed over this material by means of an aspirator. The conidiophores in certain cases 



