MISCELLANEOUS 429 



trations of the salt in the soil injure plants growing in it; 2.1 ppm of the sul- 

 fate in the sandy loam slightly retarded the growth of roots and tops of 

 soybean, wheat, alfalfa, buckwheat, rye grass, corn, tobacco, and tomato, 

 while 8.5 ppm was very injurious to these plants. The first dosage would 

 amount to 4.2 pounds per acre, considering plow depth of soil; the latter 

 would be 17 pounds per acre, considering the thallous sulfate, and much 

 less considering only the thallium. Wax beans were somewhat more resist- 

 ant. The type of injury also varied with the kind of plant. In corn the 

 tissue between veins of the leaves was killed; in soybeans, wax beans, and 

 buckwheat tissue along the veins was damaged ; in rye and wheat this was 

 true all over the plant; and in alfalfa it was limited to basal tissue. 



Studies on Lilium, Gladiolus, and Dahlia 



Storage of pollen and hybridization. In breeding work it is often desir- 

 able to keep pollen in a fully viable condition for considerable periods in 

 order that crosses may be made between plants flowering at different times. 

 It is also sometimes desirable to ship pollen to distant points for breeding 

 work. Following the earlier experiments on the effect of humidity and 

 temperature on the life span of pollen, Pfeiffer ^^' *'•*• ^'^ in order to facilitate 

 breeding experiments on Lilium, hybrid Amaryllis, and Gladiolus attempted 

 to determine good conditions for pollen storage in these genera. She later 

 made a study of Cinchona pollen. ^^ 



The viability of the pollen was tested on a synthetic medium when possi- 

 ble and in some cases on stigmas of living plants. In the latter cases the 

 development of fruits and set of seeds were the criterion of viability. The 

 pollen was stored at 10° C (50° F) with various constant humidities of the 

 atmosphere, at sub-freezing temperatures in gelatin capsules, and in gelatin 

 capsules wrapped in paraffined paper without humidity control. Also the 

 pollen was sealed in evacuated tubes and stored at various temperatures. 

 Humidity controls were obtained by storing in desiccators over saturated 

 solutions of various salts, as well as by using various concentrations of 

 H2SO4 as well as CaClo. The following are the saturated solutions used 

 with the relative humidities produced by each: 



Magnesium chloride: 35 per cent humidity at 10° C (50° F); 33 per cent at 20° C (68° F). 

 Calcium chloride: 38 per cent humidity at 10° C (50° F); 32.3 per cent at 20° C (68° F). 

 Potassium carbonate: 44 per cent humidity at 18.5° C (65° F); 43 per cent at 24.5° C 



(76° F). 

 Potassium thiocyanate: 47 per cent humidity at 20° C (68° F). 

 Sodium dichromate: 52 per cent humidity at 20° C (68° F). 

 Magnesium nitrate: 56 per cent humidity at 18.5° C (65° F). 

 Ammonium nitrate: ca. 68 per cent humidity at 10° C (50° F); 64 per cent at 20° C 



(68° F). 



For all pollens studied, thorough desiccation over concentrated H2SO4 or 

 CaCla was injurious. In general, proper humidity of the atmosphere in 

 the 10° C (50° F) storage greatly lengthened the longevity of the pollen. 



