56 



APPENDAGES TO PLANTS. 



organs are somewhat doubtful ; but we sliould not infer be- 

 cause tlie design for wliicli they were formed is in some meas- 

 ure concealed from us, tluit tliey were nuide for no purpose oi 

 exist by mere accident ; it would be impious for us to imagine 

 that all the works of God which we cannot comprehend are 

 useless. 



There are various vegetable organs which have been called 

 by the general name of ajypendages ; they are the following : 

 stipules^ 2yricMes^ tliorns^ glands^ stings^ scales^ tendrils^ jpxibes- 

 cence^ and Iracts. 



a. Stijndcs are membraneous or leafy 

 scales, usually in pairs, at, or near the base 

 of the leaf or petiole. They are subject to 

 the same laws of venation, and perform tlie 

 same offices as leaves. They sometimes 

 develop buds in their axils. "When they 

 grow from the stem they are the rudiments of leaves ; when 

 from the base of the petiole, they are the undeveloped leaflets 

 of a pinnate leaf. AYe see therefore that stipules are modified 

 or transformed leaves. The stij^ules furnish characters used in 

 botanical distinctions. They are various in their forms and 

 situations, are found in most plants, though sometimes wanting. 

 In the garden violet, viola tricolor (Fig. 63, a a), the stipules 

 are lyrate-^yinnatificl., while the true leaf (b) is oblong and 

 crenate. The most natural situation of the stipules is in j)airs, 

 one on each side of the base of the foot-stalk, as in the sweet-pea ; 

 some stij^ules fall off almost as soon as the leaves are expanded, 

 but in general they remain as long as the 

 leaves. Fig. 64 shows a portion of a branch 

 of a species of willovf ; I represents j^art of 

 a single petiolate leaf; s 5, stipules ; 5, bud 

 in the axil of the leaf. 



h. Prickles arise from the bark ; they con- 

 sist of hardened cellular tissue, and are re- 

 moved with the cuticle ; they have not like 

 the thorn connection with the wood, nor do they disappear by 

 cultivation ; they are straight, hooked, or forked. They are 

 usually found upon the stem, as in the rose ; but in some cases 

 they cover the petiole, as in the raspberry ; in others, they are 

 found upon the leaf or the calyx, and in some instances, upon 

 the berry, as in the gooseberry. 



c. Thorns^ or spines, are distinguished from prickles by 

 growing from the woody part of the plant. Although the bark 

 may be separated from a thorn-bush, the thorn will still remain 

 projecting from the wood. 



Fig. C4. 



a. Ftipulos — h. rrickles— c. Thorns. 



