188 Physiologie. 



Shull, G. A., The longevity of submerged seeds. (Plant 

 World. XVII. p. 329—337. f. 1 — 2. 1914.) 



Many problems of plant distribution involve the question of 

 the retention of vitality by seeds. Dryness, moderate and uniform 

 temperature, and the partial or complete exclusion of oxygen have 

 been recognized as favorable to longevity, and the question has 

 never hitherto been seriously raised regarding the longevity of 

 seeds under conditions unfavorable to the long retention of vitality, 

 such as extremes of temperature, or lack of oxygen with abundance 

 of water. The author placed several lots of seeds on a layer of soil 

 at the bottom of separate jars and filled the jars with water. The 

 seeds were thus submerged and kept in a cool, dark room. After 

 565 days, one of the jars was drained and the seedlings of six 

 species were identified among those that appeared. Eleven monihs 

 later, another jar was drained and seedlings of six species appeared ., 

 two of which were not in the list of those identified previously. 

 Four and one half years after submergence, a third jar was drained 

 and seedlings of eleven species appeared. A little less than seven 

 years after submergence, another jar, which just previous to drai- 

 ning had been subjected to two sharp freezes through accident, 

 was drained and exhibited three species of seedlings, with the 

 possibility not excluded that others might have appeared had they 

 not been killed by the freezing. • H. E. Pulling. 



Vinson, A. E., The effect of climatic conditions on the 

 rates of growth ofdate palms. (Botanical Gazette. LVII. p. 

 324-327. 1914.) 



By the System adopted by the writer in studying the effect of 

 climate of the rate of growth of date palms, the maximum error 

 did not exceed one-quarter inch. In addition to the leaf measure- 

 ments, daily records were kept of maximum and minimum atmos- 

 pheric temperatures, and of soil temperatures at one foot, three 

 feet, and five feet below the surface. A curve was constructed, 

 representing the total daily amount of heat received. Assuming 

 some empirical temperature (50° F.) as that below which no marked 

 growth takes place, and using this as a base line on the thermo- 

 graph Sheet, the areas lying above this line represent, at least rela- 

 tively, the heat available for growth. 



The curve representing the weekly heat-time areas, when plotted 

 along with those representing the growth of the palms, coincides 

 in general with them, with one exception. Both years the rate of 

 growth was maintained late into the fall considerably in excess of 

 the amount of heat available. 



The Chief relations of temperature to the rate of growth of date 

 palms according to the writer's measurements are: first, the period 

 of maximum growth coincides with that of highest minimum rather 

 than with that of highest maximum temperature, and this falls 

 during the summer period of highest relative humidity; second. the 

 rate of growth throughout the entire year is, in most cases, in 

 Proportion to the heat time units over 50° F. 



The rate of maturation of the fruit is probably influenced by 

 the same factors as the rate of growth of the foliage. High mini- 

 mum temperature seems to be also a more important factor in 

 determining the maturation of the fruit than high maximum tem- 

 peratures. M. J. Sirks (Haarlem). 



