REST PERIOD STUDIES WITH SEEDS 33 



was apparently too severe, and this tended to reduce the total per- 

 centage of germination so that it was only slightly greater than that 

 following the 12-hour treatment. This principle holds good in ether- 

 izing both woody and herbaceous plants. If the dose is severe enough 

 to be injurious, growth is quick but the percentage is apt to be low. 



Treatment of Seeds of Herbaceous Plants. During the winter of 

 1912-13, while working with seeds of woody plants, some additional 

 experiments were carried out with seeds of herbaceous plants. The 

 seeds used were mostly those of common vegetables which had been 

 purchased from a commercial seed house and kept in ordinary storage 

 until January. The treatments were made during the months of 

 January and February. Since a large number of treatments were to 

 be given, only a comparatively few species could be used. The species 

 employed were: Indian corn (Zea Mays, L.), Lima bean (Phaseolus 

 lunatus, L. var. Macrocarpus, Benth.), kidney bean (Phaseolus vul- 

 garis, L.), watermelon (Citrullus vulgaris, Schrad.), squash (Cucur- 

 bita maxima, Duchesne), spinach (Spinacia Oleracea, L.), radish 

 (Raphanus sativus, L.), okra (Hibiscus esculentus, L.), and onion 

 (Allium Cepa, L.). The agents used for forcing growth were ether, 

 freezing, soaking, and combinations of these treatments. Whenever 

 ether was used in a combination treatment, it was always the last 

 treatment preceding planting. The quantity of ether used per unit 

 of space and the methods of making the treatments were the same 

 as described under the head of "seeds of woody plants," (page 26.) 

 The freezing was done with a salt and ice mixture, the temperature 

 being lowered to 5 to 10 Centigrade, and the seeds exposed to 

 this temperature for twenty-four hours. The soaking was done in 

 tap water at room temperature. 



All germination tests in this series of experiments were carried 

 out by spreading the seeds between sheets of filter paper in wooden 

 plates. These plates were kept in an enclosed space (moist chamber) 

 over a sand bench in the greenhouse. The approximate temperature 

 was 22 C altrio the actual temperature at times varied considerably 

 from this figure. 



The object of the test was not only to find out the general effects 

 of ether and frost on different kinds of vegetable seeds and to what 

 extent germination is hastened by them, but by means of combinations 

 of the treatments to find out to what extent germination may be in- 

 fluenced by varying the conditions under which the ether and frost 

 are applied. 



The following review shows in detail the exact treatments to 

 which each set of seeds of the different species was subjected. 



