

CHAPTER V. 



SAP AND SECRETIONS. 



In a former Chapter we have enumerated the van 

 ous substances by which plants are nourished, 

 and we have now seen through what pores this nutri- 

 ment is absorbed, in what cells it is elaborated, and 

 through what vessels it passes from one organ to anoth- 

 er. We are next to trace this food, which is abstract- 

 ed from the soil only in a fluid state, through its various 

 changes, to learn in what way it contributes to the 

 developement of new organs, and to the formation of 

 ihe vegetable secretions. 



The water in which the roots of a plant are immers- 

 ed is gradually absorbed, and during the season of ve- 

 getation, it ascends through the vessels of the stem 

 with great rapidity and with great force, but still lim- 

 pid, tasteless and inert, possessing only the properties 

 of the pure water from which it was derived. This 

 fluid constitutes the Sap. In some plants and at certain 

 seasons it is particularly abundant. If wounded in the 

 spring previous to the expansion of their buds, the sap 

 of the Vine, Maple or Birch, flows profusely, but at 

 mid-summer, after the leaves are fully developed, the 

 " tears of the Vine'' are comparatively few. It is not 

 unusual in this country to collect one or two hundred 

 pounds of sap from a single Maple of ordinary size, and 

 we are told that a Birch tree when wounded, has been 

 known to discharge a quantity equal to its own weight. 



