PHENOMENA OF GERMINATION. 467 



found that peas in swelling could overcome a pressure of 18 

 atmospheres, corresponding to a height of the mercurial column 

 of 13.5 metres. 



1215. The influence of oxygen upon the absorption of water 

 bj' the seed is not marked, as will be seen by the following 

 experiment : ' — 



200 fresh seeds of red clover were placed in pure water for 20 

 hours ; 200 more were placed in water into which oxygen gas 

 was conducted ; 200 more in water through which carbonic acid 

 gas was conducted for a while and then the water covered with 

 a layer of oil to exclude the air. The results, so far as swelling 

 is concerned, were as follows : — 



Seeds in water 83 per cent swollen. 



" " with oxygen .... 86 " " 



" " " carbonic acid . . 71 " " 



1216. The oxygen absorbed by seeds in germination was 

 thought by Schonbein to undergo the active or ozone modifica- 

 tion. By his experiments the seeds of two plants, Cynara Scol^'- 

 mus and Scorzonera Hispanica, were shown to possess to a con- 

 siderable degree the power of converting atmospheric oxygen 

 into ozone. 



1217. Oily seeds absorb a large amount of oxygen. Siewert 

 has pointed out the fact that the neutral oil of the rape-seed very 

 soon after access of oxygen and water to it possesses an acid 

 reaction. Oleic acid can absorb at ordinary temperatures about 

 twenty times its volume of oxygen. 



1218. Nutrient matters must become liquid before they can be 

 utihzed bj' the embryo. Some of these in the form in which 

 they are stored up in seeds are soluble in water ; such are tlie 

 sugars, dextrin, and a part of the albumin. The other nutrient 

 matters, such as starch, the oils, and most nitrogenous sub- 

 stances, must undergo changes before they can enter into solu- 

 tion. Some of these changes have already been alluded to in 

 Chapter XI., and are here presented in brief review. 



1219. The conversion of starch into soluble matters is eflfected 

 in the seed bj' means of one or more " ferments." In the pro- 

 cess of malting,^ which consists essentially in forcing germination 

 up to the point of protrusion of the radicle and then checking it, 

 the starch appears to undergo little change. But if the ground 

 malted grains are kept in water of a temperature of 68° C. for 



1 TSTobbe : Handbuch der Samenkiinde, 1876, pp. 102, 103. 



2 See Watts's Dictionary of Clieniistry, under " Beer." 



