SEEDS WEEDS. 639 



The average for both tests is 35.8 per cent. 



An examination of lot 5 showed the seeds were of a dull cohn", giving 

 tlie impression tliat tliey were not properly (nired when placed in the 

 bottle, to which fact may be due the low vitality. 



The vitality of seeds buried in the soil, W. J. Beal {Agl. Sri., 8 

 {1894), Ko. G-0, pp. 2S3, ^^.S'i).— in 1879 the author buried 20 lots of oO 

 seeds each of iil species of plants, mostly weeds. The seeds were 

 l)laced in 8-oz. bottles, mixed with sand and buried at a depth of 20 in., 

 the open mouths of the bottles slanting downward. Sets of these 

 seeds were dug up at the expiration of 5, 10, and 15 years, and tested 

 for their vitality. The last year's test of germinatiou is reported upon 

 as follows: Ragweed, chess, fireweed, spotted spurge, cockle, round 

 mallow, red oak, arbor vita^, and white clover did not show any ger- 

 minated seeds; pigweed and broad-leaved plantain, 1 seed each; pigeon 

 grass and chick weed, 3 each; black mustard and smartweed, 4 each; 

 mayweed, 5; evening x^rimrose, C; narrow dock, 7; purslane, 9; pep- 

 per grass, 17; nmllein, 18; and shepherd's purse, 21. 



The influence of moisture and temperature on the process of 

 germination, W. Detmer {U. 8. Dept. A<jr., Weather Bureau Bui. 11, 

 pt. 2, lipt. Internat. Meteorolog. Congress, isjjs, pt. 2, p. 22). — The author 

 summarizes the results of many years devoted to the study of the germi- 

 nation of seeds, and reviews the i^hysiological phenomena attending 

 germination. 



In the process of turgescence, internal as well as external work is 

 performed and heat is liberated. 



'• [The antlior] mixed potato starch and pea meal of accurately kuowu temperature 

 ■with water of the same temperature. A striking increase of temperature followed 

 at once. If potato Hour is dried and after cooling brought in contact with water 

 the temi)erature will rise at once more than 6 degrees. In every imbibition jirocess, 

 therefore, as well as during the turgescence of seeds, there is a condensation of the 

 water which has penetrated between the molecules of organisms, and this must pro- 

 duce a liberation of heat." 



[The rise of temperature produced when a licpiid penetrates a mass 

 of line particles is not due to the condensation of the liquid by the 

 particles and the liberation of latent heat by compression, as is main- 

 tained by Sachs and most I )tanists. It is a thermodynamic phenom- 

 enon consequent on the conversion of a solid mass of water into a 

 great number of thin films, i. e., into a great area of surface, as Avas 

 first denionstrated by Thomson in 1859 and especially by Van der 

 Mensbrugghe in 1870.'] The fact that numy individual seeds of the 

 same crop do not easily absorb water and germinate, but in some cases 

 delay this process for months and even years, is shown to have a very 

 important bearing on the perpetuity of the species. Measurements are 

 giVen of the amount of water absorbed by seeds,^.the increase of vol- 

 ume, the pressure, and the amount of work done. The seeds of some 



jpul, Belgian Acad., 1876, or L, E. D, Phil. Mag., 187^, 



