BOTANY. 459 



of the corolla differ in almost every species ; and varieties with- 

 out number in the markings of this part of plants occur in cul- 

 tivated species. In cultivation a flower is said to be double, 

 when from excess of nourishment the stamina become petals. 



The seedy or ova of vegetables, is formed at the base of 

 the pistil in an organ termed the ovary (ovarium^) to which 

 it is attached by a small stalk or filament. When the seed has 

 attained to maturity this filament dries up and breaks, and the 

 ovary opens in various ways, according to the species, for the 

 escape of the seed. The part at which the seed has separated 

 from the ovary is indicated by a small mark or scar, called fe- 

 nestra, hilum, or umbilicus. In some seeds this scar is of 

 considerable size ; in others scarcely visible. The seed is com- 

 posed of certain coats or tunics, inclosing a kernel or nucleus, 

 also consisting of distinct parts. When these coats are stripped 

 off, the nucleus is brought into view. It consists, as in the 

 bean and most other seeds, of two distinct parts, the lobes or 

 cotyledons, and the radicle and plume. Such seeds as have 

 two lobes or cotyledons, are named Dicotyledonous, and form 

 a great division in the arrangement of plants which has for its 

 foundation the structure of the seeds. Seeds which have but 

 one cotyledon or lobe are named Monocotyledonous ; and of 

 this division the seeds of wheat, barley, and the grasses afford 

 familiar examples. A third group of plants, including many 

 of the lower tribes, are considered from their minuteness to be 

 entirely destitute of cotyledon, and these have been termed 

 Acotyledonous. This description includes the whole of the class 

 Cryptogamia of Linnaeus ; but some observers have considered 

 the Filices and Musci as not falling under this division. 



The duration of the life of vegetables is various. Some spring 

 up, ripen their seeds, and die within the year. These are term- 

 ed annual plants. Others take two years to reproduce their 

 seeds, and these are called biennial ; while others which go on 

 increasing for a term of years are denominated perennial. The 

 life of an annual plant, however, may be prolonged to the se- 

 cond year by preventing it from flowering. Monocotyledonous 

 plants generally flower only once, though they grow for years 

 before that period ; and though many of the Dicotyledonous 

 - plants survive for centuries, yet the successive growths are 

 merely annual superpositions. 



