46 



THE FACTORS [Part I 



which are chiefly concerned with the oecological optimum. As an example, 

 the following tabular statement prepared by Detmer ' is here reproduced : 



CARDINAL POINTS OF GERMINATION (after Detmer). 



Minimum. Optimum. Maximum. 



7-S°C. 27° C. 34" C. 



5 * 287 42-5 



9-S 33-7 46-2 



7-8 24 36 



1-8* 21 28 



1-8 21 28 



9-5 337 46-2 



9 28 36 



. 137 337 46-2 



* Figures too high. 



Pinus sylvestris . 

 Triticum vulgare. 

 Zea Mays . 

 AInus glutinosa . 

 Lepidium sativum 

 Linum usitatissimum 

 Phaseolus multiflorus 

 Gleditschia triacantho 

 Cucurbita Pepo . 



This table shows very clearly that the cardinal points of germination are 

 higher for plants from warm countries than for those from cold ones. Bui 

 these figures are too high in some cases, and by no means properly repre 

 sent the great inequality of temperatures which are effective during germina 

 tion in different climates, for, on the one hand, they do not deal with an) 

 purely tropical plants, and, on the other hand, some of the minima fo 

 temperate plants are too high. The degrees of temperature given for the 

 minima by F. Haberlandt are more instructive. Sinapis alba, Camelin; 

 dentata, Trifolium hybridum, and Medicago sativa not only germinatec 

 between 0° and 1° C, but also made considerable further progress ii 

 development. Of plants from hot countries, Solanum Melongena, Nicotian; 

 Tabacum, and Cucurbita Pepo germinated between 11° and 16° C, bu 

 Cucumis sativa, C. Melo, and Theobroma Cacao only above 16° C. Ulotl 

 observed the germination of several grasses, Cruciferae and Papilionacea( 

 at 0° C, but the process was very protracted. Kerner placed glass tube 

 containing earth and seeds in a sprirtg, the temperature of which remainei 

 constant at 2° C, and he found that numerous alpine plants germinate 

 even at this low temperature. 



Growth depends on conditions of temperature similar to those require 

 for germination, which partially consists of processes of growth. Ther 

 are plants on alpine heights, but especially in the polar regions, that caj 

 grow considerably at a temperature approaching the freezing-point. Thu 

 the flowers of Soldanella alpina break through the snow, and those c 

 Anemone vernalis, Crocus vernus, and other species appeared to me t 

 be quite as accommodating, as I found theni in half-melted snow ; bt 

 owing to direct insolation, even through thin layers of snow, a highe 

 temperature than 0° C. may be reached in such cases. Even more remark 



' Lehrb. d. Pflanzenphysiol., p. 269. 



