32 



PRINCIPLES OF PLANT CULTURE 



which the air is kept very moist and the surface of the soil 

 never becomes dry. 



53. The embryo. — The plantlet is visible in the seed. 

 If we soak seeds of the four kinds shown in Figs. 8 to 11, or 

 of other kinds, in water until they are fully swollen, and 

 then carefully dissect them, using a magnifying glass when 

 necessary, we may observe that the plantlet is present, 

 compactly folded up in the seed. Germination (28) is 



Fig. 14. — Cross-section of germinating Indian corn grain. A endo- 

 sperm ; Cot cotyledon ; Cau root ; PI plumule. Slightly magnified. 



really little more than the unfolding and expansion of this 

 plantlet. The plantlet as it exists in the seed is called 

 the embryo. 



54. The endosperm (also called albumen) . — From the 

 section of the corn grain shown in Fig. 14, it appears that 

 in this seed, unlike the pea, bean and pumpkin, the plantlet 

 and seed-case do not make up the whole bulk of the seed. 

 The remaining part shown at A consists mainly of cells con- 

 taining starch grains and oil drops, which serve as food for 

 the plantlet during germination, since active protoplasm 



