Effect of Location of Seed upon Germination

Abstract

The influence of parent trees upon the size and germination of Jeffrey pine seeds has been shown in a previous paper.' The marked results obtained from that work resulted in the present study, in which it has been sought to determine the value of seeds from different parts of the pine cone; and to decide what relation, if any, exists between the position of the seed and germination. The cones used were collected from Pinus Jeffreyi trees on the eastern slope of the Sierras in Lassen County, California, in September i919. No attempt was made to choose the trees from which the cones were taken, except that the trees were young and growing thriftily, considering the site upon which they stood. The cones were grouped according to size in three divisions, based on the gross characteristics of length, breadth, and weight. They were dried slowly in a room at air temperature, and as they opened the seeds were extracted. The cones were divided into three sections of approximately equal size, to be known as the upper, middle, and lower portions. The seeds were carefully collected and graded into three classes, large, medium, and small, using ocular means of determining the size and comparing one seed with another. Inasmuch as a number of individuals helped to determine the size of the seed grains themselves, the individual variation from this source was very largely eliminated. The seeds were cleaned, counted, and weighed, each lot kept separately, and sufficient seeds to carry out the test taken at random from each lot. To determine the germination, a number of each lot of seeds were sown in cans containing a uniform depth of soil and covered by an approximately equal depth of sand in each case. As previous work has shown that for Jeffrey pine a soil moisture content of about I5 per cent gives the best results, frequent weighings were made to keep the moisture content of the samples a constant at this figure. The result of this study is presented in tables I-VII.