SEEDLINGS. 



309 



free end and slips off at the stem end. The next coat within, which is also 

 hard and shining black, splits open at the opposite end, that is at the stem 

 end. It usually splits open in the form of three ribs. Next within the inner 

 coat is a very thin, whitish film (the remains of the nucellus, and correspond- 

 ing to the perisperm) which shrivels up and loosens from the white mass, the 

 endosperm, within. In the castor-oil bean, then, the endosperm is not all 

 absorbed by the embryo during the formation of the seed. As the plant 

 becomes older we should note that the fleshy endosperm becomes thinner and 

 thinner, and at last there is nothing but a thin whitish film covering the green 

 faces of the cotyledons. The endosperm has been gradually absorbed by the 

 germinating plant through its cotyledons and used for food. 



586. How the embryo gets out of a pumpkin seed. We should not fail 

 to germinate some seeds of a pumpkin or squash. Some of the seeds should 



Fig. 403. 



Seedlings of castor-oil bean casting the seed coats, and showing papery remnant of the 

 endosperm. 



be sown in the soil, and some on damp sphagnum covered with moist paper, 

 or between the folds of a damp cloth, first soaking them for ten to twelve 



