io8 THE PLANT WORLD. 



branches because they are necessarily permanent. There are, how- 

 ever, a few woody climbing plants whose tendrils are a modification of 

 parts that in other plants are annually deciduous; but these parts be- 

 come permanent by virtue, or as a correlative part, of that modifica- 

 tion. In the cases referred to the tendrils are modified stipules, and 

 the plants bearing them are severals pecies of Smilax, all of which are 

 known by the common name of Greenbrier. 



At the time of their falling, deciduous leaves of woody plants usually 

 separate easily from the stem by a clearly defined incisure, leaving 

 only a scar upon the plant to mark the place of the former attachment; 

 but although the leaves of Smilax are deciduous, their separation from 

 the stem takes place quite differently. Two tendril-stipules arise from 

 the basal portion of the petiole of the newly forming Smilax leaf and, 

 like other tendrils, soon seize upon adjacent objects. If, when autumn 

 comes, this leaf should separate from the stem in the same manner as 

 do other deciduous leaves, the stipule-tendrils would go with it, and 

 the plant then be without support. 



To provide for continuous support by its tendrils the leaves of 

 Smilax are shed in a peculiar manner. The basal part of the petiole, 

 including that portion from which the stipule-tendrils arise, clings as 

 tightly and permanently to the stem from which it grew as if it were 

 really a part of it. In autumn, when other plants shed their leaves, 

 the petiole of smilax weakens, not at its base, as is the case with other 

 leaves, but at a point just beyond the stipule-tendrils. The petiole 

 breaks off there and the blade is cast by the chilly winds among the mul- 

 titude of other fallen leaves, while the tendrils remain as permanently 

 on duty as if they were modified branches of the plant. They never 

 loosen their hold upon the stem, and cease to perform their office of 

 tendrils only in consequence of decay, after years of service. 



These two cases of modification of stipules are remarkable, not 

 only for their obviously protective uses, but for the extreme difference 

 in the purpose of each. They are moreover remarkable because 

 stipules are not a constant part of leaf -bearing plants. They are en- 

 tirely wanting in a large proportion of such plants, and are abortive 

 or inconspicuous in many others. Indeed, when stipules are present 

 they are rarely of any apparent service to the plant upon which they 

 grow, except as accessory foliage. 



Smithsonian Institution. 



The herbarium, letters, manuscripts, drawings, etc., belonging 

 to the late M. S. Bebb, the well known authority on Salix, have be- 

 come the property of the Field Columbian Museum of Chicago. 



