REMARKS ON VEGETABLE PHYSIOLOGY. 



and at whatever time, we examine the sap of a plant, we find that it contains organic 

 principles which cannot come from the soil, because they do not exist there; such as starch; 

 sugar, gum, malic, citric and tartaric acids, albumen, &c. These substances are diluted 

 with a good deal of water, and mixed with a little carbonic acid and carbonate of ammo- 

 nia which are contained in the water of the soil. Even in the colls of the roots which 

 first receive the moisture of the soil, it is chemically changed, assimilated, and the sap is 

 most decidedly not flowing in special vessels but passing upwards from cell to cell, and thus 

 it is in every new cell which is being developed by the formative chemical processes. Noth- 

 ing remains for the leaves to assimilate." 



This you see is an utter denial of the ascent of the sap in special vessels, of its elabora- 

 tion in the leaves, or descent in the bark. Now if he be right, how is it possible, that, 

 when the ascent of the sap is obstructed by the compression of the stem as with a ligature 

 the upper part, which is less in contact with the sap than the lower part, can increase 

 much more rapidly in size? The example to which I have referred is that of the branch 

 of a plum tree encircled by the wire of a label. This branch is four years old, and during 

 the whole of last season and part of the one previous, this wire has been so tight that no 

 enlargement of the wood under it could take place, the consequence is that the part just 

 above the wire is one inch greater in circumference than that below it, so much greater 

 have been the deposites of new matter above than below. Besides it happened that on 

 one side the wire did not press so firmly, nor so soon as on the other, and on that side 

 of the part below the wire, we find the last layer of wood three times as thick as on the 

 other side, where the pressure was first and greatest, and the separation more complete. 



The annexed drawing represents the branch referred to, A the large por- 

 tion above the wire, and B the smaller portion below. C, D, the point en- 

 circled by the wire. On the side D, the wire admitted of greater expan- 

 sion, and there the upper and lower lip of the wound project almost equal- 

 ly. On the side C, the upper lip is a regular perpendicular wall 3-lG of an 

 inch deep, the surface of the lower part being quite even. On the cut sec- 

 tion E, we find the last ring of wood on the side A, D, B, 3 times as large 

 as on the other, on account of the partial communication existing at the 

 point D. 



Does not this furnish a pretty strong indication that the formation of new layers of 

 wood, is a downward process, and that it depends upon the leaves. 



Dr. ScHLEiDEN accounts for such cases by saying, " As water is continually exhaled by 

 plants in proportion to the motion, drj^ness and warmth of the air, so the sap becomes 

 concentrated, and thus interrupts the endosmotic process towards the other cells; this ac- 

 tion is continued naturally downwards towards the roots, by which new watery and un- 

 assimilated fluids are absorbed. If this stream of crude sap* is artificially interrupted in 

 its course from below upwards, the sap in the upper part becomes more concentrated, and 

 its organizing power increased. This is the simple fact which lies at the foundation of all 

 the phenomena which are brought forward to support the groundless h3'pothesis of a de- 

 scending bark sap. The two most important facts upon this subject are : 1. The magic 

 ring (ringing fruit trees.) 2. The action of grafts. 



" If from the circumference of a branch or tree, a ring of bark be removed, the upper 

 part Avill bear richer blossoms and fruit ; the latter will ripen quicker, the leaves will be 

 thrown off sooner, and the trunk will become thicker and stronger than in the part below 

 the cutting. All this is completely explained in the foregoing facts, without makin 



* In a previous quotation the existence of a "crude sap" is denied. 



