134 SEVENTEENTH REPORT. 



LIGUT AXL) TYCNIDIA FORMATION IN THE 

 SPHAEROPSIDALES. 



BY EZRA LEVIN. 



As a result of a hint* obtained elseAvhere, exi>eriments were 

 initiated for the purpose of testinj^ the effect of light upon various 

 members of the Sphaeropsidales, 



A representative number of tonus were collected at Ann Arbor 

 from as many genera as possible. A pure culture was obtained 

 (always using the single spore method) transferred to a medium 

 upon which pycnidia would be formed, and finally a set of cultures 

 arranged so that all environmental conditions were equal except 

 that one set was placed in the light and the other in the dark. 



The material was brought into the laboratory and identified. The 

 twigs or leaves were placed in moist chambers. After 24 hours, 

 plates of corn-meal agar were poured in the usual manner. A 

 pycnidium was cut out with a sharp scalpel and broken up in a 

 tube (I) of agar. Three transfers were made with a platinum loop 

 from tube I to tube II. Then three loops from tube II into tube 

 III and finally poured into sterile petri dishes. The spores were 

 immediately found under the low power of the microscope and 

 marked. These were cut out and transferred to tubes of agar, 

 usually five transfers being made. 



Corn-meal agar was found to l)e the best medium for pycnidial 

 production. In order to keeji cultures in the dark and still allow 

 for the nuiintenance of identical conditions of other environmental 

 factors, the following method Avas used. The tubes were wrapped 

 in black paper but not sealed. These were placed side by side with 

 the tubes of the same species in the light. All trials for botli light 

 and dark were made in duplicate. 



In this preliminary report just a few of the forms whicli have 

 shown a decided difference in pycnidial formation when growth in 

 light and dark will be reported. 



(Considering 10 as arbitrarily representing the largest numl)'.'r 

 of pycnidia formed in any the cultures, the data can be given briefly 

 as follows.) 



♦That light is essential for pycnidia formation in some forms was first shown by 

 Mr. O. IT. Coons in this hiborntory, working witli Aposphaeria fusco-maciilans Sacc. 

 tlie Posults soon to be published. 



