164 WAYaiDE WEEDS. 



spiral vesselsj wMch, although drawn out in thig 

 instance like an uncoiled spring. He, in their ordi-. 

 nary condition, with their coils close together, 

 mingled with the tube-Kke and other vessels, the 

 cells being disposed amongst or around them in 

 various ways. Pine as these vessels seem, yet are 

 they sufficiently strong, if carefully drawn out, to 

 support the one half of the severed leaf (Fig. 101), 

 when retaining no connection with the other half 

 beyond that afforded by the almost invisible spiral 

 coil. In the leaf the distinction between the vessel- 

 tissue and the ceU-tissue is so strongly marked, 

 that even the beginner cannot fail to note the 

 former as making up the veins of the leaf, and the 

 latter as filling up all the intermediate spaces. As 

 you may suppose, the use of the cells and vessels of 

 plants is chiefly to permit and promote the circula- 

 tion of the sap, or of the fluids generally ; but the 

 former especially are also destined to serve as 

 store-bags for the secretions peculiar to the tree or 

 {»lant, 



