114 VEGETABLE SAP. 



scopes of the highest powers, describe the ligneous 

 fibres as being formed of " elongated cells attached by 

 their ends to each other." Solly. 



The Sap. The sap of plants is that fluid which 

 fills and assists to distend the cells and vessels. It is 

 of various consistence ; in some plants it is thin and 

 watery, easily congealed by cold and evaporated by 

 heat ; in others gummous, and in many resinous. 

 Besides the difference in consistence, the sap contains 

 many essential qualities, as sugar, starch, resin, &c. 

 with a thousand combinations of these and other 

 bodies in various degrees. 



The juices become inspissated and almost stagnant 

 during winter or when the plant is at rest, and regain 

 fluidity and motion on the return of spring, or of the 

 growing season. So completely fluid is the sap soon 

 after the commencement of the growth that it flows 

 freely from wounds. During summer its excess is 

 consumed by the lengthening shoots, numerous leaves, 

 and swelling fruit. In autumn it becomes gradually 

 thickened in consistence, and is at last again arrested 

 in its motion by the cold of winter. It is often ob- 

 served, however, that in the last mentioned season, 

 even after the leaves of deciduous trees have fallen, 

 and all outlets of the growth shut up, that a few 

 warm days will so liquefy the sap, that it will again 

 flow from wounds ; more especially if the roots are in 

 a moist situation. 



That the peculiar qualities and characteristics of 

 the sap are elaborated by the plant itself, as has been 



