68 



DOMESTIC BOTANY. 



stipules of India-rubber and other fig trees. Sap circu- 

 lation is however readily observed in the jointed stems 

 of limeworts (chara), the jointed hairs of the stamens of 

 Virginian spiderwort, the spongial roots of frog-bit, and 

 in the leaves of the Valisneria spiralis, Potamogeton, and 

 other water plants. In the first three each joint has its 

 own circulation, which is easily seen by loose globules 

 of chlorophyll being moved by the current, thus form- 

 ing an interesting spectacle. Although the portion 

 examined is removed from the living plant, the cir- 

 culation nevertheless continues ; and if a small branch 

 of chara is placed under favourable circumstances (in a 

 vial, for instance) new joints will be seen to form, and 

 it becomes a plant. It may therefore be supposed that 

 a plant consists of a multitude of independent organisms, 

 which as a whole unite and contribute to its welfare; but 

 each on being separated is endowed with the vital power 

 of becoming a plant, as, for instance, a twig, a small bit 

 of wood with its bark, a bud, a leaf, portion of a leaf or 

 root, are well known to gardeners as the means for pro- 

 pagating plants. Thus plants have the advantage over 

 animals, and although they have not the power of moving 

 from place to place, yet on considering what has been 

 stated of them in the preceding pages as regards their 

 growth, organs, and functions, their analogy to animals 

 is evident. From many circumstances they are not de- 

 void of knowing what is necessary for their good ; they 

 fatten when well fed, the roots of trees find their way to 

 water and new soil, the aerial roots of orchids and aroids 

 direct their course to the nearest surface; and it has been 

 observed in hothouses, when hung near a moist surface, 

 they take a horizontal direction, even forming a right 

 angle. Twining plants or tendrils also direct their course 



