STRUCTURAL BOTANY. 



CHAPTER XII. 



THE SEED. 



172. The seod is the perfected ovule, having an embryo 

 formed within, which is the rudiment of a new plant similar in 

 all respects to the original. The seed consists of a nucleus or 

 kernel invested with the integuments or coverings. The outer 

 covering is the testa, the inner the tegmeti, as in the ovule. The 

 latter is thin and delicate, often indistinguishable from the testa. 



173. The testa is either membranous (papery), coriaceous 

 (leathery), crustaceous (horny), bony, woody, or fleshy. Its 

 surface is generally smooth, sometimes beautifully polished, as 

 m Columbine, Indian-shot (Canna), and often highly colored, 

 as in the Bean ; or it may be dull 



and rough. It is sometimes winged, 

 as in Catalpa, and sometimes clothed 

 with long hairs, as in Silk-grass 

 (Asclepias). Such a vesture is called 

 the Coma. Cotton is the coma of 

 the Cotton-seed. 



201 



174. The coma must not be confounded with 

 the pappus (' 104), which is a modification of the 

 calyx, appended to the pericarp, and not to the 

 teed, as in the achenia of the Thistle, Dandelion, 

 and other Composite. Its intention in the econ- 

 omy of the plant cannot be mistaken ; serving 

 like the pappus to secure the dispersion of the 

 seed, while incidentally as it were, in the case of 

 the Cotton-seed, it furnishes clothing and em- 

 ployment to a large portion of the human race. 



175. The aril is an occasional appendage, par- 

 tially or wholly investing the seed. It originates 



after fertilization, at or near the hilum, where the OI U()Uon - 

 seed is attached to its stalk (funiculus). Fine ex- 

 amples are seen in the gashed covering of the Nutmeg, called mace, and in the scarlet 

 coat of the seed of Staff-tree. In the seed of Polygala, etr., it is but a small scale, entire 

 or 2-cleft, called caruncle. 



170. The position of the seed in the pericarp is, like that of the ovule, (.reel, ascending. 

 jwndulouSi etc. ( 149). Likewise in respect to its inversions, it is orthbtropous, andtro- 

 pous, ampJiUropous, and campylotropous ( 141), terms already defined. The anatroppna 

 ie by far the most common condition. 



198. Aril of Nutmeg dunce). 199, Seed of 

 ittalpa. 200, Seed of Willow. 201, Seed 



