Influence of Certain Carbohydrates on Green Plants 19 



sterilization of seed 

 The method of seed sterihzation employed was one developed in the 

 Laboratory of Plant Physiology by Wilson (1915) . In brief it is as follows: 

 Ten grams of calcium hypochlorite (chloride of lime, or bleaching powder) 

 is shaken up with 140 cubic centimeters of water, and after the mixture 

 has stood for a short time the supernatant, clear liquid is decanted off 

 and filtered. It is now ready for use. The seeds to be sterilized are 

 placed in a test tube or similar vessel and the hypochlorite solution is 

 added. The tube or vessel is tightly stoppered, and the seed is left in 

 the solution for a few to twenty-four hours. The treatment of the various 

 seeds will be described in detail later for each experiment. 



STERILIZATION OF MEDIA AND CULTURE VESSELS 



The culture vessels, containing the culture solutions, were sterilized 

 under steam pressure. The smaller vessels were heated in an autoclave 

 for twenty-five minutes at fifteen pounds pressure, while the larger con- 

 tainers were sterilized for one hour at ten pounds pressure in a large steam 

 sterilizer such as is used in canning factories. Even at the prolonged 

 exposure in the latter case, contamination of the saccharose cultures 

 occasionally occurred, due to the development of submerged hyaline 

 colonies of a bacterium. This organism occurred only in the saccharose 

 cultures. Its appearance was evident five or six days after sterilization. 

 All cultures showing the contamination were rejected. 



sowing THE SEED 



For sowing the seed in certain of the experiments a small copper spoon 

 was used. This was made of a small strip of copper, which was v/orked 

 into a perforated spoon large enough to hold two vetch seeds and fitted 

 with a wooden handle. The spoon was sterilized by immersion in alcohol 

 and then flaming. The seed was transferred directly from the bleaching- 

 powder solution to the culture vessels much as one might make transfers 

 of bacteria or fungi. In many of the experiments each lot of seed was 

 sterilized separately in small test tubes, each test tube holding the seeds 

 for a single culture. This method was necessary when the weight of the 

 seed was to be accurately determined. 



UNIFORMITY OF SEEDS 



In all the experiments the seeds used were carefully selected as regards 

 uniformity in appearance and size. Only plump, vigorous-looking seeds 



