SnrULLsi A.NU TENDRILS. 



09 



leaves of the Mn^^no^ia Hotoropliylla, hence the reason for the 

 fall of leaves on the lower part of a stem first. It would seem 

 fn^m tlie nl>ove, that tlie duration of leaves depends upon the 

 time that they are capable of adapting themselves to the stem 

 ou which they fijrow. Some can exist only for a few days, 

 others throufrh the summer, while the evergreens are so con- 

 structed as not to he dislodjxcd hut hy the growth of the wood 

 of the succeeding year. 



Section 7. — Stipules and Tendrils. 



75. At the base of inanv loaves no moot with t\\o leaf-like 

 organs, separated hy the substance of the base of llic petiole, 

 which are called »S7/y)M7c^. Stipules frequently tall oft' upon 

 the development of the leaf, when ihey are called c aducous, 

 at othiTs they remain as long as the leaf, and are called per- 

 sistent. In the former ti^oy ai'e attarho»] only by iheirbasc 

 to the stem, in the latter they are connected with the petiole 

 and fall only with it. In opposite leaved plants the stipules 

 corresponding to tlie two leaves are generally united, forming 

 but two stipules instead of four. Tl.o bop affords an exam- 

 ple of this kind. The stipules are in many respects analo- 

 gous to leaves, and even have buds in their axils, as in the 

 Peach, and in some instances are very much 

 like them in appearance, as in the Pea, (fig. 

 \ %'^.) In others they bear no resemblance to 

 the leaves hut are simple membranous appen- 

 dages, as in the Hickori/, or fine bristles as in 

 the Cherrv. Thev assume a grpat variety of 

 appearances, by vario'Ts modifications of 

 structure and attachment. In the rose they 

 are attached to the petiole forming a leaf-like 

 mamin to that orjran. In the Polygonum 

 and Rhubarb they form a sheath round the 

 stem by the union of their edges, and are 

 then called ochre.f., (fig. 04.) In some 

 plants they become hardened and conical 

 and tbrm spines. In climbing plants they 

 often lengthen into a slender thread-like ap- 

 pendage, and become the organ by which 

 the plant attaches itself to objects over 

 which it climbs, thus fornu'ng for the plant 

 j^^ liie means of support. But however vari- 

 ous may be their aj)peaiances, and however 

 unlike in structure, yet if they originate from the base of a 

 leaf tbcv arc stipules. • ^ 



