34 STIPULES. TENDRILS. 



[Whatever arises from the base of a petiole, or of a leaf, if sessile, oc- 

 cupving the same place, and attached to each side, is considered a 

 stipule. The appearance of this organ is so extremely variable, some 

 being large and leaf-like, others being mere rudiments of scales, that 

 botanists are obliged to define it by its position, and not by its organization. 



Stipules, the margins of which cohere in such a way that they form a 

 membranous tube sheathing the stem, are called ochrea. Example, the 

 rhubarb. Lindley.] 



28. The filamentous appendages, known under the name of 

 tendrils, which twine themselves round neighbouring bodies, serve 

 to sustain weak and climbing plants, are frequently petioles 01 

 stipules, modified in a particular manner, but they are also often 

 formed by the peduncle of flowers that have proved abortive in 

 development. 



29. According to their duration on the stem, the leaves are 



Caducous, when they fall early, as in the plane tree. 



Deciduous, when they fall belbre the new leaf appears, as in the horse- 

 chestnut, and most other trees. 



Marcescent, when they wither before falling, as in the oak, and many 

 other trees. 



Persistent or Evergreen (Sempervirens), when they remain on the ve- 

 getable one winter or longer, as the iv.y, the pine, the. myrtle, the com- 

 mon laurel, &c. Plants of this kind are called evergreens. 



The various shapes of leaves, and the names given to them, as 

 well as the variety of their margins, may be seen in the following 



EXAMPLES OF THE FORMS OF SIMPLE LEAVES. 



The side or edge of the leaf in which the petiole is inserted, is 

 'ermed the base, and the opposite extremity, the apex of the leaf. 

 A linear leaf folium lineare (fig* 17). (Folium, 

 Latin, a leaf; lineare, Latin, line-shape.) The two 

 edges straight and equidistant throughout, except at the 

 two extremities. The Jester linearifolius, the star-flower, 

 as well as Indian corn, and the grasses generally, have 

 leaves of this kind. 



When it embraces the stem it is vaginate or 

 sheathing. 



fig. 17. A subulate leaf folium subulatum (fig- 

 LINEAR. 18). (Subulate, from the Latin, subula, an 

 awl awl-shaped.) Linear at bottom, but gradually 

 lessening towards the top, and ending acute. The 

 Phascum subulatum, one of the mosses, and the jonquil, Fig- 

 have a leaf of this description. SUBULATE. 



28. What are tendrils ? 



29. What is the difference between a caducous and a deciduous leaf? 

 'Caducous, from the Latin, cado, I fall. Deciduous, from the Latin, de- 

 cido, I fall off.) When are leaves said to be marcescent? (Marcescent, 

 from the Latin, marceo, I wither.) What are persistent leaves 1 (Per- 

 sistent, from the Latin, per, through, and sisto, I remain.) 



