XVi INTRODUCTION. 



and septicidal, when it opens at the ventral suture, or through the partitions. 

 When it opens transversely, the upper portion falling oif entire, like a lid, the 

 dehiscence is circumscissile, 



90. A Silique is a slender two-valved capsule, with two parietal placentae con- 

 nected by a persistent false partition. A short and broad silique is a Silide. 

 These are peculiar to the Mustard Family. 



91. A Pepo is the fleshy indehiscent fruit of the Gourd Family, with the seeds 

 often embedded in the pulpy placentae. 



92. A Pome is the indehiscent fruit of the Apple or Quince tribe, where the 

 cells are enclosed in the enlarged and fleshy tube of the calyx. 



93. A Berry is an indehiscent fruit, with the seeds embedded in soft pulp. 



94. A Drupe consists of one or more hard or bony cells, called the Pula- 

 men, covered with a fleshy or pulpy coat, called the Sarcocarp; as the Peach, 

 Holly, &c. 



95. An Achenium is a small, dry, one-seeded, indehiscent fruit, the walls of 

 which do not adhere to the enclosed seed. When these are closely united, it 

 becomes a Caryopsis; or when the walls are thin and bladder-like, and open 

 irregularly, a Utricle, 



96. A Nut is a dry, indehiscent fruit, with hard or bony walls ; as the Acorn 

 and Hickory-nut. 



97. A Samara is a dry, indehiscent fruit, with its walls expanded into a wing ; 

 as that of the Maple and Elm. 



98. The collective fruit of the Pine is called a Cone or Strobile. 



10. The Seed. 



99. The Seed is the matured ovule, and contains the Embryo, or the rudiment 

 of a future plant. The outer coat, or Integument, is called the Testa. It varies 

 greatly in texture, and is occasionally furnished with hairs, which either cover the 

 entire seed, or form a tuft {Coma) at one or both extremities. 



100. The terms employed in describing the ovule are chiefly applicable to the 

 seed. The foramen of the ovule, which is closed in the seed, becomes the Mi- 

 cropyle, and is always opposite the radicle of the embryo. The scar left on the 

 seed by the separation of the cord is the Hilum. It is sometimes enveloped in 

 a false covering, originating, during its growth, from the cord or from the pla- 

 centa. This is called the Aril. 



101. The Testa includes either the embryo alone, or an additional nutritive 

 substance, called the ABmmen. , 



102. The Embryo consists of the Radicle, the Plumule, and the Cotyledons. 



103. The Radicle is the first joint of the stem. In germination, it elongates 

 at one end to form the root, and at the other, from a minute bud {Plumule), to 

 form the stem. It is inferior when it points to the base of the pericarp, and su- 

 perior when it points to its summit. 



104. The Cotyledons are the seed-leaves. The embryo of the Exogenous 

 Plants bears two of these, placed opposite (rarely three or more in a whorl), 

 while that of Endogenous Plants bears only one. Hence the former are called 

 dicotyledonous, and the latter monocotyledonous. 



105. When the embryo is exposed to the combined influence of air, heat, and 

 moisture, it develops into a growing plant. This is termed Germination. 



