FUNCTION.] ACCUMULATION OF SAP. 327 



operation, is unknown, and is not perhaps susceptible of 

 absolute proof. 



Upon this subject we have a very interesting paper by 

 Mr. Honninger, of Tubingen (Botanische Zeitung, 1843) who 

 has recorded his experiments with the Vine, &c. In summer 

 he found most of the vessels empty ; sap, however, was still 

 present, but only in the most internal parts ; the prosenchy- 

 matous cells of the wood also were still full of sap. By 

 ferrocyanide of potassium and sulphate of iron, he found in 

 the shoots of Lycium barbarum that the most external layers 

 of vessels (tubular tissue) were, for the most part, stained blue, 

 the middle ones empty, and the most internal, blue throughout. 

 The same botanist made further experiments with numerous 

 plants, which he first caused to absorb ferrocyanide of potas- 

 sium, and of which he afterwards made sections, which he 

 placed in a solution of sulphate of iron, because he found 

 this more convenient and more certain, than when he allowed 

 them to imbibe the latter solution. The results which he 

 deduces from his inquiries are 1. That in cellular plants 

 without a central series of elongated cells, there is no special 

 organ for the transmission of sap. Mr. Honninger made his 

 observations only on lichens, not on other cellular plants* 

 2. That in all vascular plants the sap is carried upwards 

 solely through the vessels (tubular tissue). The grounds for 

 this last proposition are so conclusive, that Link thinks we 

 may look upon it as a settled question. 



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 imperfect 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. 

 Knight, in a valuable paper upon this subject, 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 well 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 manner, if a fruit tree is by any 



