9G 



ELEMENTS OF STRUCTURAL BOTANY. 



(Fig. IGO). If, as in Shepherd's Purse (Fig. 

 29), the capsule is short and broad, it is 

 called a silide. If the capsule opens 

 horizontal y, so that the top comes 

 off like a lid, as in Purslane (Fig. 

 Fig. 161. 161), it is a, 2)yxis. 



156. Any dry, one-seeded, indehiscent fruit 

 is called an achene, of which the fruit of 

 Buttercup (Fig. 14) is an example. In 

 Wheat the fruit differs from that of Butter" pjg j^o 

 cup in having a closely fitting and 

 adherent -pericav]}. Such a fruit is called 

 a caryojysis or grain. A nut is usually 

 syncarpous, with a bard, dry peri- 

 carp. A winged fruit, such as that 

 of the Maple (Fig. 162), is called a 

 samara or key. 

 Seed. The seed has already been de- 

 scribed as the fertilized ovule. It consists of a nucleus, 

 enveloped, as a rule, in two coats. The outer one, 

 which is the most important, is known as the testa. 

 Occasionally an additional outer coat, called an aril, is 

 found. In the Euonymus of Canadian woods, the aril 

 is particularly prominent in autumn, owing to its bright 

 scal■le^ colour. The stalk, by which the seed is attached 

 to the placenta, is the funiculus, and the scar, formed 

 on the testa where it sepai*ates from the seed-stalk, is 

 called the hilum. In the Pea and the Bean this scar is 

 very distinct. 



158. Germination of the Seed. When a seed is 

 hghtly covered with earth, and supplied with warmth 

 and moisture, it soon begins to swell and soften, owing 

 to the absorption of water, and presently bursts its 



Fig. 162. 



157. The 



