134 



th:: leaves. 



sides of the stem and point in opposite directions (127, Fig. 107, 

 210, &c). They are verticillate, or whorled, when there are three or 

 more leaves in a circle (verticil or tohorl) upon each node ; in which 

 case the several leaves of the circle diverge from each other as much 

 as possible, or are equably distributed around the whole circumfer- 

 ence of the axis (Fig. 134, 211). The first of the three is the 

 simplest as well as the commonest method, occurring as it does in 

 almost every Monocotyledonous plant (where it is plainly the normal 

 mode, 128), and in the larger number of Dicotyledonous plants 

 likewise, after the first or second nodes (Fig. Ill*, 121). It 

 should therefore be first examined. 



m 238. Alternate Leaves. This general term 



for the case where leaves are placed one after 

 another, obviously comprises a variety of 

 modes as to the particular position of succes- 

 sive leaves. There is, first, the case to which 

 the name is mo-t applicable, viz. where the 

 leaves are alternately disposed on exactly op- 

 posite sides of the stem (as in Fig. 157) ; the 

 second leaf being on the side farthest from the 

 first, while the third is equally distant from 

 the second, and is consequently placed directly 

 over the first, the fourth stands over the 

 second, and so on throughout. Such leaves 

 are accordingly distichous or two-ranked.* 

 They form two vertical rows : on one side 

 are the 1st, 3d, 5th, 7th, &c. ; on the op- 

 posite side are the 2d, 4th, 6th, 8th, and so 

 on. This mode occurs in all Grasses, in many 

 other Monocotyledonous plants, and among 

 the Dicotyledonous in the Linden. A second 

 mode is 



239. The trisdehous or three-ranked ar- 

 rangement, which is seen in Sedges (Fig. 



* In the course of the summer the leaves of Baptisia pcrfoliata, which are 

 really five-ranked, often appear to be monostichous, or one-ranked ; but this is 

 owing to a torsion of the axis. 



FIG 202. Piece of a stalk, with the sheathing bases of the leaves, of a Se<lg"-Grass (Carex 

 Crus-corvi), showing the three-ranked arrangement. 2C3 Diagram of the cross-sec tiou of the 

 same, showing two cycles of leaves. 



