THE SEED. 



43 



the milk- wood, or with nioro doliciito libros, as in (cotton (Fi<^. 05). Somo 

 seeds have an additional covering, more or less exi)andod in i'onn, termed 

 an arillus, or aril; of such character is the mace of nutmeg and the 

 scarlet pulp enclosing the seeds oi the woody bitter-sweet [Cduiitrus scaii- 

 dcns), so nuxch used fov winter decoration. 



All tlie expansions of the external seed-coat are evidently designed to 

 favor the distribution of the seeds. 



The scar loft where the seed-stalk separates is termed the hilum ; the 

 minute orifice through which the pollen-tube entered, now closed up, is 

 termed the micropyle. 



Tlie kernel is tlio essential part of the seed. In many seeds it is all 

 embryo — that is, a minute folded-up plantlet ; in others it comprises not 



-'" .- 





FlQ. 91. — Winged sccil of tlio pino. 



Fin. O.'i. — C.jttoii ficed. 



only the embryo, but a mass of nourishing matter in which this is im- 

 bedded, termed the albumen. 



The albumen is composed of stai'ch, gluten, oily matters, etc., and is 

 designed to nourish the young plantlet during the early stages of its de- 

 velopment, before its roots have taken firm hold of the soil. It should be 

 borne in mind that this ditVers in every essential particular from animal 

 albumen. 



The embryo, or germ, is the embryo plantlet whose development we 

 have studied in the bean and Indian corn. It is distinguishable into throe 

 parts, namely, (1) the radicle, called also and more properly the caulicle, 

 or rudimentary stem, to one end of wliioli are attachetl (2) the cotyle- 

 dons, or seed-leaves, between which is the rudimentary bud termed the 

 (3) plumule, while the other end becomes the descending axis. 



And here we leave this branch of our siibject, having outlined, in a gen- 

 eral way, the history of flowering plants from their germination in the seed 

 to their reproduction in seed again. 



From this history that of flowerless or cryptogamous plants 

 fliffers in many essential particulars, but most of all in their earliest and 

 latest stages, in germination, and in reproduction. This subject cannot be 



