APPENDIX. 75 



be 2*01 meters in diameter, and 6*33 meters in circum- 

 ference, while, in reality, the said stem was only 25 centi- 

 meters in diameter above the root -stalk. 



Before I follow Mirbel's researches further, I must 

 subjoin a few words to the foregoing. In the explanation 

 of the structure of the Palm-stem I have called attention 

 to two circumstances, to the course of the fibres, and to 

 the alteration of their structure and size in different parts 

 of their course. To the latter point, Mirbel, in advancing 

 the preceding calculation in opposition to my view, 

 paid no attention, but it was necessarily required that 

 lie should have done so, to afford any useful result. 

 Mirbel says the Palm-stem swollen in the middle is a 

 complete contradiction to my theory. The fact that such 

 stems occur was well known to me, but by itself it was 

 not of sufficient importance to give rise to a different 

 theory. That with the development of the stem and the 

 increase of the force of its vegetation, the upper leaves 

 are larger than the lower, and a greater number of fibres 

 run from them into the stem, than from the lower ; that 

 the stem must consequently acquire greater diameter at 

 the base of these leaves than at the base of the lower 

 leaves all this is exceedingly simple. This increased 

 thickness must be continued to the lower part of the stem, 

 and the latter thus acquire a conical shape if the vascular 

 bundles run down without change of thickness to the 

 base of the stem, but by no means if, at the place where 

 they appear beneath the surface of the stem, they be- 

 come so slender, that in spite of their accumulation they 

 still form no equivalent for the greater size of their 

 upper ends, situated higher up in the stem. The plates 

 of my ' Anatomy of the Palms' afford evidence of how 

 considerable this attenuation is ; they are drawn with the 

 Sommering's reflector, the relative sizes of the various 

 parts of the same figure are therefore accurate, and a 

 comparison of the vascular bundles with the thin fibres 

 lying beneath the rind, shows that the transverse section 

 of the latter is frequently a hundred times smaller than 



