148 THE CANADIA?r HORTICIDT>TtrRJST. 



in cramming- a; quart of water into a pint cup ; perhaps, in order to 

 accommodate the sap, th« roots are supposed to be as large and capa- 

 cious as the trunk and head of the tree ; in sbort, that there is as much 

 tree underground as above. Whence the idea sprang into existence 

 that the sap retires to the roots on tlie approach of wiiiter, it is not 

 now possible to say, but its very general popular acceptation is an 

 evidence of the way in which false views gain currency l?eca«se some 

 one ventures to make the asseition, ami the public mind stops not 

 even to weigh the probabilities, much less to investigate the ground 

 upon which it rests. Surely the time has come when we should cease 

 to accept assertions upon trust, and demand tlie facts on which they 

 are based. Having these, we can consider the theory, and if it does 

 not suit us we can make one for- ourselves. 



Now,, in this matter of the sap, by which we mean all tlie tlviids. 

 which are contained in the interior of a tree, the facts are these: if 

 the trunk be cut in spring, the sap will run out ; in summer, autumn, 

 and winter it will not, except under exceptional circumstances. But 

 nevertlieless the sap is in motion in the summer and autumn, and 

 winter too ; nay, save when extreme cold may for a time interfere with 

 its flow, it is always in motion ; and the reason why it ruins out of the 

 trunk in the spring is because it is then present in much greater abun- 

 dance than at any other season of the year. During the summer, when 

 the tree is covered with foliage, the leaves are evaporating large 

 quantities ot the fluid parts of the tree into the air, while another 

 portion is being elaborated and converted into the tissues and structure 

 of the tree, producing what we call growth. When the autumn has 

 come, what with the evaporation and solidification that has taken 

 place, the interior of the tree has become comparatively dry, so that 

 the quantity of sap has become so greatly diminislied that it no longer- 

 exudes when an incision is made. Our readers are, at least many of 

 them, aware that if a branch be cut off from a grape vine in spring 

 when the buds are starting, the sap will run out quite freely, produc- 

 ing what is called bleeding ; but if the same branch w^ere allowed to 

 remain until trlie leaves on the vine have became fully expanded, then 

 if it be cut off no bleeding will take place. The reason is, that the 

 evaporation which is taking place in the leaves has exhausted the 

 supply of sap to such an extent that there is no surplus in the vine to 

 escape in that way. 



