CONDITIONS FOR SPROUTING 7 



primary leaves and they also contain the food supply. They are 

 united by a very short embryonic stem, known as the hypocotyl 

 (i.e., the part below the cotyledons). Of course, this hypocotyl 

 is very short, but from one end arises the primary root, which 

 is known as the radicle, while at the opposite end we find the 

 minute bud known as the epicotyl (i.e., the part above the 

 cotyledons). These parts are covered by the seed coats which 

 show certain markings. The scar, marking the point of attach- 

 ment, is known as the hilum. On one side of this hilum we 

 find a slightly raised ridge known as the raphe and on the other 

 side we find a minute opening known as the micropyle. (Fig. 2.) 



The seed of the castor plant is dicotyledonous like the bean, 

 but the food is stored as an endosperm around the embryo, as 

 in the case of the corn, instead of in the cotyledons, as in the 

 bean. The arrangement of the various parts of the embryo is 

 the same as in the bean, but the cotyledons are very thin and 

 show their leaf-like character very distinctly. The entire em- 

 bryo is surrounded by the food supply which is enclosed within 

 the seed coats. At the tip of the seed there is a mass of spongy 

 material, covering the hilum. It is called the caruncle and will 

 be discussed later. (Page 12.) The embryos of monocoty- 

 ledonous see4s are usually smaller than those in dicotyledon- 

 ous seeds. The food supply in the former is always found sur- 

 rounding the embryo, while in the latter it may be either around 

 the embryo or in the enlarged cotyledons. Embryos in which 

 the food is in the cotyledons are usually more advanced in their 

 development before ripening than those in which the food sur- 

 rounds the embryo. In the former the embryo has absorbed 

 its food supply before ripening, while in the latter it must be 

 absorbed during germination. (Fig. 3.) 



Conditions for Sprouting. When the seeds of most plants 

 are ripe they can be stored in a dry place and kept for a long 

 time, and then used for planting. But of course, the seeds of 



