OF STIPULKS. 



45 



tLe leaf, between tlie stem and the petiole, in 

 which case they are said to be axillar, as in 

 Melianthus major. The stipules vary greatly 

 in their nature and consistence. Thus they may 

 he foliaceoitu, or similar to leaves, as in the com- 

 mon agiimony ; membranotis as in the fig and 

 magnolia ; spinescent, or thorny, as in the jujube 

 and the gooseberry. 



With respect to duration, some fall off before 

 the leaves ; as in the common fig and the lime. 

 Others are merely caducous, or fall at the same 

 timeas the leaves, as is the case in thegenerality of 

 plants. Lastly, there are others which continue 

 for a longer or shorter time after the leaves have 

 fallen ; as in the jujube, the gooseberry, &c. 



The use of the stipules appears to be to pro- 

 tect the leaves before their expansion, as is evi- 

 dently showTi by their relative disposition in the 

 buds of some families of plants. 



The Tendrils or 34. 



Cirrhi. Those are cer- 

 tain appendages, fig. a, b, 

 generally filamentous, 

 situated on different parts 

 of the plant, simple or 

 branched, and wliich 

 twist themselves, in a 

 spiral form, around 

 neighbouring bodies, 

 thus serving to support 

 the stem of weak and 

 climbing plants. " 



Tendrils are in all cases abortive organs. Some- 

 times, they are floral peduncles, which have been 

 greatly elongated, as in the vine, and are occa- 

 sionally seen to bear flowera and fi-uits; some- 

 times they are formed of petioles ; and at other 

 times they are altered stipules, or even abortive 

 twigs. Not unfi-equently, the leaves themselves 

 are rolled >ip at the extremity, and thus consti- 

 tute a kind of tendrils, as in the pink. The re- 

 lative position of the tendrils deserves to be care- 

 fully attended to, as it indicates the organ for 

 which they are substituted. Thus in the vine 

 they are, like the clusters of flowers, opposite to 

 the leaves, which shows them to be abortive 

 clusters. They are axillar in the passion-flowers ; 

 petiolar in lathi/rus latifoliits and fximaria vesica- 

 ria; peduncular in the vine; stipular in certain 

 species of smilax. Lastly, they may be simple, 

 as in Bryonia alba, or branched, as in cob<ea scan- 

 dens. 



Tlie name of claspers is given to the kind of 

 roofs which climbing plants sink into the bodies 

 on which they raise themselves, as in the ivy ; 

 while that of slickers is given to the very slender 

 filaments which are met with on the surface of 

 claspers, and which appear to be destined to 

 absorb the nutritious parts contained in the body 

 into which they are inserted. 



Spines or thorns d, are sharp-pointed organs, 



formed by the prolongation of the internal tissue 

 of the vegetable; while prickles c, originate 

 only from the most ex- 

 ». temal part of plants, that 



is, from the epidermis, 

 from which they may 

 be detached with the 

 greatest ease. 



The origin and nature 

 of the spines are not 

 less variable than their 

 seat. They are substi- 

 tuted for the leaves in 

 certain African species of 

 asparagus, and for the 

 stipules in the j uj ube and 

 the goosebeiTy. Very frequently they are merely 

 abortive twigs ; as in the sloe, which, on being 

 transplanted into a good soil, changes its spines 

 into twigs. The trunk of some trees is so cov- 

 ered with spines as to render them inaccessible. 

 According to their situation and origin, they 

 are cauline, when they spring from the stem ; as 

 in the cactus: terminal,\\\ieut\\ey are developed 

 at the extremity of the branches and twigs ; as 

 in the sloe ; axillar, when they are situated in 

 the axilla of the leaves ; as in the citron: iufra- 

 axillar, when they spring from beneath leaves 

 or twigs ; as in the goosebeny. 



Prickles have been considered by some physio- 

 logists as indurated hairs. They adhere but 

 slightly to the parts on which they are observed, 

 and may easily be detached from them, as is seen 

 in the rose. The modifications which they pre- 

 sent with respect to situation, form, &c. are the 

 same as in the spines. 



Among other appendages of plants, may bo 

 mentioned the singular cup of the neptnthes 

 distillatoria, or pitcher plant. Attached to the 

 extremity of its long slender leaf, is a body ex- 

 actly resembling a water pitcher, furnished with 

 a lid or covering, which opens and shuts accord- 

 ing to the absence or presence of the sun, or the 

 degree of heat. In this cup is contained a 

 quantity of pure water, secreted from the juices 

 of the plant. What purpose this secretion serves 

 in the economy of the particular vegetable, has 

 not been ascertained ; a more particular account 

 of the plant will be given afterwards. 



CHAP XI. 



NUTRITION OF VEGETABLES, AND ASCKNT 

 OF THE SAP. 



We have now finished the description of the 

 organs which contribute to the nutrition of the 

 plant, including the roots, stem, and leaves, with 

 the various minute cells and vessels of which 



