VEGETABLE PHYSIOLOGY, Gl 



internal state of the seed itself, or to the circumstances in which 

 it is placed, with regard to surrounding circumstances. 



1. Maturity of the seed. The first condition necessary to 

 germination is, that the seed must have reached maturity. Unripe 

 seeds seldom germinate, hecause their parts are not yet prepared 

 to form the chemical combinations on which germination depends. 

 There are some seeds, however, whose germination is said to 

 commence in the very seed vessel, even before the fruit is ripe, 

 and while it is yet attached to its parent plant, as for example, 

 the garden radish, the lemon and the pea. But these are 

 examples of rare occurrence ; though it is sometimes necessary 

 to sow or plant the seed almost as soon as it is fully ripe, as in 

 the case of the coffee bean ; which will not germinate unless it 

 be sown within five or six weeks after it has been gathered. 

 But most seeds if guarded from external injury will retain their 

 germinating faculty for a period of many years. 



2. Exclusion of light. The second condition is that the seed 

 sown must be secluded from the action of the rays of light. 

 This has no doubt been long known to be a necessary condition 

 of germination, if we regard the practice of harrowing or raking 

 in of the grains or seeds sown by the farmer or gardener as being 

 founded upon it. But it does not seem to have engaged the 

 notice of the scientific, or to have been proved by direct and 

 intentional experiment till lately. Ingenhoutz and Senebier 

 ascertained by experiment that seeds germinate faster in the 

 shade than in the sun, and hence concluded that light is prejudi- 

 cial to germination. But it remained to be determined whether 

 the prejudicial effect was to be attributed merely to the light, or 

 partly to the heat accompanying it. From the experiments of 

 Ingenhoutz and Senebier, the injury appeared to be occasioned 

 by the light only, because the comparative experiments in the 

 shade and in the sun, were made at equal temperature, as 

 indicated by the thermometer. With this conclusion, however, 

 though apparently legitimate, M. Saussure professes to be 

 dissatisfied, because the thermometer placed even under the 

 recipient is, in his opinion, incapable of indicating the actual 

 degree of the heat of the solar rays impinging on the surface of 



