26 ELEMENTARY BOTAKY. 



of this arrangement are very numerous, as the Apple, Oak, 

 Elm, Willow, Dock, etc. If two leaves occur at each node, they 

 are said to be opposite (Fig. 7), as the Maple, Ash, Pepper- 

 mint, Catnip, etc. Sometimes there are three or more leaves 

 at each joint, as in Cleavers (Galium), Trumpet-weed (Eitpato- 

 rium purpureum), etc. In this case the leaves are said to be 

 verticillate (Fig. 8). In the Pines and Larch the needle- 

 shaped leaves are in clusters, that is, they are said to be fas- 

 ciculate. If leaves grow from the base of a stem, but appear 

 to come out of the ground, they are radical (Lat. radix, root). 

 Those leaves inserted in the stem are caiiline (Lat. caulis, 

 stem). 



6. On a straight, leafy shoot of an Elm, Cherry, Apple, Oak, 

 Willow, etc., pass a thread from the lowest leaf to the one 

 next above, and continue it around the stem in the same 

 direction to the successive leaves above. The thread will be 

 seen to take a spiral course ; the leaves are therefore spiral 

 in their arrangement on the stem. In the Elm the third 

 leaf stands directly over the first, and to reach it the thread 

 has passed once around the stem, or, as is usually said, 

 the cycle is complete when the third leaf is reached, and it 

 is expressed by the fraction \. The numerator denotes the 

 number of turns ; the denominator the number of leaves en- 

 countered. Experimenting in a similar manner with Alder, 

 the fraction ^ is obtained, and with the Cherry f. In the lat- 

 ter case the stem would be encircled twice before a leaf is 

 found (the sixth), which is inserted directly over the first, 

 and five leaves are contained in the cycle. In a similar man- 

 ner the fraction f with the Flax, ^ with the Flea-bane, ^ 

 with the Houseleek, H with cones of some Pines would he 

 obtained. 



7. A leaf may have three parts, namely ; the Blade or 

 Lamina, which is the expanded portion ; the Petiole, which 

 is the stem of the leaf; and Stipules, which are the append- 

 ages at the base of the petiole (Fig. 9). The stipules are very 

 often wanting, in which case the leaf is said to he exstipulate. 

 If the blade is inserted directly on the stem (wliich is the case 



