264 The Sap. 



But the sap is also diffused laterally through the cellular lissue 

 and this with great rapidity, as will be apparent upon placing a 

 branch in a colored infusion, which will ascend and descend in 

 the manner just stated, and will also disperse itself laterally in 

 all directions round the principal channels of its upward and 

 downward route. That there must be an exceedingly rapid (low 

 of sap in many plants, is evident from the great loss they ex- 

 perience by perspiration, all of which must be made good by 

 fluid absorbed by the roots. With this function are connected 

 all the phenomena that attend transplantation. If a growing 

 plant is removed from one situation to another in the summer, it 

 will die, because its spongioles will be so much destroyed as to 

 be incapable of absorbing fluid so fast as it is given off by the 

 leaves, and hence the system will be emptied of fluid. But if a 

 plant is growing in a pot it may be transplanted at any season 

 of the year, because its spongioles being uninjured will be able 

 to counterbalance the loss caused by perspiration as well after 

 transplantation as before, if not better. 



"With regard to the vessels through which this universal diffu- 

 sion of the sap takes place, it has already been stated that its up- 

 ward course is always through the woody fibre, and probably 

 also through the ducts, and that it passes downwards through the 

 woody fibre. But there can be no reasonable doubt that it is also 

 dispersed through the whole system, by means of regular tubes or 

 vessels expressly for its conveyance, which are invisible to our 

 eyes even aided by the most powerful glasses. 



The accumulation of sap in plants appears to be attended with 

 very beneficial consequences, and to be deserving of the especial 

 attention of gardeners. It is well known how weak and imper- 

 fect is the inflorescence of the turnip tribe forced to flower before 

 their fleshy root is formed ; and how vigorous it is after that 

 reservoir of accumulated sap is completed. Mr. Knight remarks 

 that the fruit of melons which sets upon the plant when very 

 young, uniformly falls off; while on the contrary, if not allowed 

 to set until the stem is formed, and much sap accumulated for 

 its support, it swells rapidly, and ripens without experiencing 

 any deficiency of food in the course of its growth. In like man- 

 ner, if a fruit tree is by any means prevented bearing its crop 

 one year, the sap that would have been expended, accumulates, 

 and powerfully contributes to the abundance and perfection of 



