3 6 A. MARTINELLJ ON THE GEIIMINATION OF A SEED. 



broken up and disorganised. Tested with iodine they take a 

 reddish-brown tinge. The molecules of which the seed is composed 

 now pass from a state of comparative repose to one of inconceivable 

 activity. A certain volume of oxygen seizes upon its equivalent of 

 carbon in the starch, and carbonic acid gas is formed and given off. 

 With this, the first act of respiration by the embryo, the mysterious 

 hand of Nature arouses it from its slumber, and it becomes a living 

 plant. Throughout the period pf germination that respiratory 

 process continues ; the atmospheric oxygen absorbed by the water 

 combines with the carbon contained in the molecules of starch until 

 not unfrequently the carbon, in half the seed, is consumed in forming 

 carbonic acid gas. A loss to this extent is readily demonstrated in 

 the case of an albuminous seed such as the Buckwheat. If weighed 

 and planted, and then again weighed just at the moment when the 

 reserve materials are consumed, and after depriving the seedling of 

 the water taken up in germination, it will be found to have lost quite 

 an eighth part of a grain. That is to say, the whole of the plant at 

 this particular point of growth is only half the weight of an un- 

 pl anted seed which averages J grain minus the testa. Such 

 destruction of carbonaceous matter not only causes a considerable 

 increase in the temperature of the seed, but results in the conversion 

 of the remaining starch into dextrin or gum. Thus provided, the 

 rootlets burst through the seed coats in search of further moisture. 

 The fibrils absorb it, and the already prepared dextrin becomes 

 diluted. Forced out of the cotyledons into the central axis of the 

 j)lant, the dextrin, by taking up the elements of water, undergoes 

 an important chemical change. It is converted into grape sugar, 

 and in this way the solubility of the assimilated materials is 

 increased to the utmost degree.* 



Thus abundantly supplied with nutriment, the plumule and its 

 miniature leaves gain strength to force their way in an upward 

 direction. The liquid sap is carried by the upward current into the 

 body of the plant, and its myriad molecules yield up the secretions 

 necessary for the maintenance of its protoplasmic functions,. Then 

 the purpose of the molecules as parts of a sweet liquid comes to an 

 end. They give up the elements of water previously taken, and, 

 reverting to the same chemical composition as starch and dextrin, 

 are fixed in the plant as its final insoluble product, ceUi/lose. So 

 that a unity of nature underlies these forms. It is only a re- 

 arrangement of the same atoms that results in starch, dextrin, and 



