372 



PLANT STUDIES 



seeds being represented by the " core." In other cases, the 

 end of the stem bearing the ovaries (receptacle) becomes 

 enlarged and pulpy, as in the strawberry. This effect 

 sometimes involves even more than the parts of a single 

 flower, a whole flower-cluster, with its axis and bracts, be- 

 coming an enlarged pulpy mass, as in the pineapple. 



The term " fruit," therefore, is a very indefinite one, so 

 far as the structures it includes are concerned. 



247. The germination of the seed, — It is wrong to apply 

 the term " germination " to the renewal of activity by the 

 young plantlet within the seed, as has been shown before 

 (page 354), but in the absence of a better word it will be 

 used. This " awakening of the seed " is a phenomenon so 

 easily observed that it can hardly escape the attention of 

 any one. 



Just how long different seeds may retain their vitality — 

 that is, live in a state of suspended animation — is not very 

 definitely known. Some seeds have germinated after hav- 

 ing remained in a dried-up condition for many years, but 

 such stories as that wheat taken from the wrappings of 

 Egyptian mummies has been made to germinate are myths. 



If the structures of the seed are normal, its germination 

 will follow its exposure to certain conditions, prominent 

 among which are water, heat, and oxygen. Seeds vary in 

 the amount of water and heat absolutely needed, but for 

 terrestrial plants all the suitable conditions are supplied 

 by burial in loose, moist soil, at the temperatures which 

 prevail during the growing season. 



This so-called germination is merely a rencAval of the 

 growth of the embryo, which results in freeing it from the 

 seed coats, and in enabling it to establish itself for inde- 

 pendent living. All the conditions for growth are present, 

 namely, food material^ stored within the seed, most com- 

 monly as starch or oil ; oxygen^ to be used in respiration ; 

 water^ to put the cells in proper condition for work, and 

 to act as an agent of transfer; and a suitable tempera- 



