SEED. 



77 



Fig. 145. 



Hilum, the scar. This is that part which is commonly 

 termed the eye of the seed, and indicates the place of union 

 between it and the seed vessel, or pericarp. Through this 

 connection, it is, that the seed receives its nourishment du- 

 ring its growth. When the seed is ripe, this organ of com- 

 munication becomes dry, and separates from the parent plant 

 without injury. When the seed is planted, it is supposed 

 to imbibe moisture from the earth through the pores of the 

 hilum, arid on this circumstance its germination, or growth, 

 seems to depend. 



Pappus, Fig. 145, egret or seed down. Pappus 

 in Latin, signifies grandfather, or old man, the 

 term being originally applied to the seed down of 

 the Thistle, on account of its resemblance to the 

 grey hairs of old age. 



The pappus is commonly found attached to 

 such seeds as want the pericarp, as in the com- 

 pound flowers. The thistle, Dandelion, and Colt's "Foot, 

 (Tussilago,) are examples. It is either sessile, that is, placed 

 immediately on the seed, or furnished with a stipe, by which 

 it is elevated above the seed. 



The above figure represents the pappus of the Dandelion, 

 with its stipe ; c, the down ; a, the stipe, and b, the seed. 



Fig. 146. 



The Sessile pappus, Fig. 146, consists of the 

 down and seed only, the stipe being wanting. 

 Of this, the Thistle, (Carduus,) is an example. 



Plumose seed down, Fig. 147. The appendage 

 to the seed is so called, when the filaments, or 

 downy threads, being of considerable length, rise 

 directly from the seed, and are furnished with 

 softer filaments on each side, like a feather. 

 Sometimes this plumose appendage is formed by 

 the elongation of the style of the plant, as in the 

 Virgin's Bower, (Clematis.) When it is thus 

 formed it is called cauda, a tail. 



Fig. 147. 



What is the hilum, or scar ? What is the pappus ? To what tribes oi 

 plants is the pappus peculiar ? What is the form of the plumose seed 

 down ? W T hat is the ala, or wing of a seed ? 

 7* 



