520 ORGANOLOGY. 



fluid. If, however, we observe the processes going forward at any par- 

 ticular instant during the whole time of vegetation, it will be easily seen 

 how inconsiderable is the chemical process in the plant in comparison 

 with the strong evaporation which is constantly carried forward. Eva- 

 poration assists endosmosis by means of suction. Little has been ascer- 

 tained by botanists respecting this important question, because it is much 

 easier to dream about a system at random than to observe, investigate, 

 and experiment. 



To the mind of a correct observer there can be no doubt that the fluid 

 is not distributed regularly and normally through the vessels. A stand- 

 ing fact yet remains, which has puzzled most incorrect observers, namely, 

 the spring sap. Most observations concerning the motion of the sap 

 have been carried on in the spring on the grape-vine, and observers 

 have pursued these experiments without considering plants in general. 

 This is a perverted way of making observations. I am almost per- 

 suaded it will shortly be discovered that the spring sap, in the commonly 

 received sense of the term, does not exist at all. In the mean time 

 I would make the following observations: It is generally known that 

 if the branches of different woody plants, as Vines, Birches, Forest 

 Beeches, &c. are cut, or if their stems are pierced in the spring, a large 

 quantity of fluid escapes from the part with a power which corresponds, 

 as in the vine, to the-pressure of more than two atmospheres. If the sap 

 flows in a continuous stream, such a pressure (at least in vines whose old 

 stems have vessels sometimes 0'3 m. m. (millimetre*) in diameter) must 

 cause it to spirt out in a stream, which it never does ; and this fact is en- 

 tirely opposed to the idea of the motion of the sap in vessels. In the next 

 place, the question is certainly to be answered, Can we draw a general 

 conclusion from the injured plant to the uninjured vegetating normal 

 one ? Plants which are not cut in the spring, as vines, never allow a 

 drop of fluid to escape ; they cover themselves with leaves neither earlier 

 nor later than those which are cut, as I this year observed, and as has 

 been observed by Mr. Baumann, a botanical gardener of great experience. 

 A vine-branch which measured O01 1 m. (metre*) in diameter, and ex- 

 tended in length along the ground 1'446 m., with an almost horizontal ele- 

 vation from the soil of about 0*2 m, delivered between 1 1 A.M. of the 25th 

 of April f , and 5 P M of the 2d of May, 4550 C. Cent, (cubic centimetre*) 

 of sap ; therefore for the hour 30-33 CC. It was united with a glass tube 

 by an India-rubber band, which was fastened into an alembic by a cork ; 

 another tube, drawn out fine at both ends, also went through the cork, and 

 by this means possibly served to lessen the evaporation without making the 

 escape of the air from the alembic impossible. With another branch B. 

 (2'396 m. long and 0*10 m. thick, with a similar direction), I tied up the 

 alembic with only an India-rubber gutter, somewhat open above, so that 

 the air had free entrance to the cut surface. This branch gave out, 

 during the first six hours, less sap than the other, and ceased to bleed 

 much earlier. In the whole, I received from it 3220 CC., therefore for 

 the hour 21 '406 CC. of sap. That so great a stream of sap cannot have 

 place in the uncut and naturally growing plant, is shown by the fact that 

 such a mass of fluid can in no way escape through the dry and air-filled 

 bark. I must say that I have not been able to convince myself of the 



* A millimetre is '03937 Eng. inch ; and a metre is 39-3710 inches, and a centimetre 

 -39371 inch TRANS. 



f On the 10th and J 1th of April, in the same garden, the vine, in a favourable situa- 

 tion, had begun to blossom, and ceased on the 2d and 3cl of May. 



