OEGANS OF NTTEITION. 



133 



not the case, as the gemmule or plumule {fig. 14, n) also pos- 

 sesses rudimentary ones. The cotyledons are usually very dif- 

 ferent in their appearance from the ordinary leaves which succeed 

 them. The first leaves which appear after the cotyledons are 

 te,rm.Qdi primordial {fig. 15, d,d) ; these, and the cotyledons, gene- 

 rally perish as soon as, or shortly after the development of the 

 other ordinary leaves. The latter are called radical, when they 

 arise at, or below the surface of the ground, and thus apparently 

 from the root, but really from a shortened stem, or croxon of the 

 root as it is commonly called. Leaves are thus situated in what 

 are termed acaulescent plants, such as the Dandelion and Prim- 

 rose. The leaves which arise from the main stem are called 

 cauliiie ; those from the branches raraal ; and those from the 

 base of, or upon the flower-stalks, floral leaves or bracts. 



When a leaf arises from the stem by means of a petiole it is 

 said to be stcdked or petiolate {fig. 248, p) ; when the blade of a 

 leaf is fixed to the petiole by a point more or less within its 

 margin, as in the Indian Cress {fig. 254), and Castor Oil plant 

 {fig. 306), the leaf is peltate or shield-shaped; when the petiole 

 is absent, so that the blade arises directly from the stem, it is 

 said to be sessile {fig. 260) ; when a leaf is enlarged at its base 

 and clasps the stem from which it springs, it is amplexicaul or 

 emhracing, as in Fool's Parsley {jig. 255), or if it forms a 



Fig. 254. 



'Fig. 254. Peltate leaf of the 



Indian Cress (Tropreohtni.) 



Fig. 255. Amplexicaul petiole 

 of Angelica. 



complete sheath around it, as in Grasses generally {figs. 256 

 and 348,^), it is said to be sheathing; when a leaf is prolonged 

 as it were from its base, so as to form a winged or leafy appen- 

 dage down the stem, as in Thistles, it is decurrent {fig. 1bl)\ 

 when the two sides of the base of a leaf project beyond the 

 stem and unite {fig. 258), as in the Hare's-ear {Bupleurum per- 

 foliatum) and Yellow- wort {Chlora perfoliata), it is fcrfoliatej 



