266 BOARD OF AGRICULTURE. 



seeds, and to be, in general, much less in seeds which ger- 

 minate early. It is well known, that, at the outset of germi- 

 nation, there is a slight elevation of temperature of the seed, 

 which has been attributed to the commencino: oxidation of 

 food-substances. Tliis was shown, however, by Wiesner ^ to 

 be connected with the forcible absorption of water, and to 

 be plainly observed before the evolution of carbon-dioxide. 

 But, although liquid water is forcibly absorbed by seeds and 

 with elevation of temperature, there is some reason for 

 believing that water in a state of vapor is not absorbed by 

 them at all.^ 



The absorption of water is correlated with the absorption 

 of oxygen, and with the temperature. Coelestin Herma- 

 nauz^ has shown that access of atmospheric oxygen and 

 water, both of them essential to germination, stand in a 

 certain sense opposed to each other; and, furthermore, the 

 absorption of water is much hindered by a low temperature. 

 Lastly, according to the same experimenter, the capability 

 of germinating at all diminishes with increase of time re- 

 quired by seeds for the absorption of water. Certain inter- 

 esting experiments in regard to the slow germination of 

 seeds with hard integuments, and as to the possibility of has- 

 tening this by incisions, must be passed by without further 

 notice. The most valuable recent contribution to this part 

 of the subject is by Nobbe ^ and Haenlein, who have carefully 

 examined the integuments of certain seeds with reference to 

 their resistance to external influences which induce germi- 

 ]\ation. The results of their investigation in regard to red 

 clover may be briefly summarized as follows : The coats of 

 the need possess five distinguishable layers, which behave 

 differently in regard to water, and which vary considerably 

 in different seeds. The seat of the resistance is not, as 

 Nobbe himself formerly supposed, to be found except in the 

 more superficial layers. The percentage of " hard " or resist- 

 ing seeds was found to be, in Trifolium i^ratense. (red clover), 



1 Wien-Sitzungsb. LXIV. 1871. 



2 F. Habeiiandt. Wisseuschaftl. praktische Unters. auf dom Gebiete der 

 Pflanzenbaucs. Vienna, 1, G3. 



3 Biedermann's Centralblatt fiir Agricult.-Chemie. 187G. Bd. 10, 357. 

 * Die Landwirtbscli. Vcrsucbs-Stat. xx. 11 (1877), p. 7. 



