14 A. MARTINELLI ON THE GERMINATION OF A SEED. 



If we macerate a bean, filter the liquid and add tannic acid, a pink 

 flocculent matter casein is precipitated. Its similarity to the 

 casein of milk is so decided, that in some parts of China cheeses are 

 made from the casein of beans. From the expressed juice of the 

 potato albumen can readily be coagulated in considerable quantity. 

 Lastly, by softening a grain of barley and removing its outer tissues, 

 we come upon a layer of cells, arranged with singular regularity, 

 containing vegetable /5rm (Fig. 9). It lies in intimate connexion 

 with the starchy mass of the grain. Possessing almost the same 

 chemical composition and character as the fibrin of muscle, or the 

 casein and albumen of the egg, it is also analogous to the casein 

 of the bean and the albumen of the potato. When obtained from 

 wheaten flour, it is in a mixed condition, and closely resembles 

 freshly exuded indiarubber. 



A more complete analysis may now be made of the various sub- 

 stances referred to. Starch must be regarded as a compound of 

 three elements — Carbon, Hydrogen, and Oxygen, the two latter in 

 the proportion forming water. It consists of a number of molecules, 

 each having the composition represented by the following formula : — 

 Cg Hio O5 and is the carbonaceous portion of the seed. The other 

 constituents of the seed, fibrin, albumen and casein, which occupy so 

 considerable a place in relation to the processes of plant life, contain 

 Nitrogen in addition to Carbon, Hydrogen and Oxygen. They are the 

 principal albuminoids in the seeds already mentioned, and, although 

 so unlike in outward appearance, there is a marked similarity between 

 them in chemical composition and character. Hence they suggest 

 an ultimate identity in nature and purpose. For example, they are 

 all dissolved by potash. The solution blackens salts of lead, and 

 the presence of sulphur is thereby indicated. Nitrate of Mercury, a 

 test of great delicacy, colours them red ; its rapidity and evenness 

 of effect rendering it a striking experiment. In combustion they 

 all emit the same unpleasant odour ; while on exposure to the air 

 they rapidly putrify, and, in that condition, act as organised 

 ferments converting grape-sugar into alcohol, carbonic acid gas, and 

 other compounds. 



In contradistinction to this physiological action there is developed 

 from the albuminoids of the germinating seed a non-living ferment 

 called Diastase. To this agent is ascribed the power of converting 

 starch, which is not directly available for plant growth, into carbonic 

 acid gas, dextrin, and grape-sugar. This ferment is stated to be 



