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tablished theory, bear out Dr. Schleiden's views in a remark- 

 able manner. It is true the newly-formed tissue extended 

 from the upper lip of the cut chiefly in the downward direction, 

 and that very little appeared on the lower lip. But the 

 train of reasoning I adopt from these circumstances is that 

 of Dr. Schleiden. The flow of sap by endosmotic process from 

 cell to cell, was interrupted by the alburnum and cambium 

 being cut across on the pillar which was laid bare. It there- 

 fore diverged' laterally, and followed its natural upward 

 course, on the three pillars where no laceration had been made, 

 which accounts for no growth taking place on the lower lip. 

 On the portion of stem above the cut, a greater degree of 

 formative energy accrued, in consequence of the interruption 

 the endosmotic process met with below. The tissue thus 

 formed would rather extend itself on the vacant space under, 

 i. e., the bare pillar, than upwards, where endosmosis was less 

 vigorous, in consequence of many of the cells being filled with 

 sap of greater density. In this manner it continued to grow 

 until it reached the lower lip of the cut, where its downward 

 course was obstructed, when it spread in a lateral direction 

 over the surface of the lip, as well as upwards, until the bare 

 surface became covered over. During the whole process it 

 did not occur to me, that the young wood was formed by a 

 returning bark-sap. The growth seemed gradual and not 

 periodical. The young tissue taking a lateral and upward di- 

 rection when it met the lower lip, shows that, although the 

 tendency be downwards, it will alter. 



" A remarkable example of the permeability of the tissues 

 of plants has farther been proved through this experiment. 

 From knowing the heart-wood was dead at the part of the stem 

 which was operated on, I was desirous to ascertain whether it 

 continued so to the apex of the tree, which I had some reason 

 to suppose it did, from having about four years ago observed 

 a small portion of the top shoot dead. I, however, found the 

 heart-wood full of sap, and apparently very healthy, in a piece 



