76 THE PALM-STEM : 



that of the former. With this considerable attenuation 

 of the vascular bundles at their lower extremities, with 

 the more distant position of the upper parts of them in 

 the interior of the stem, and with the crowded position 

 of their lower filiform extremities, even if the fibres did 

 run down in the stem, the lower part of this would only 

 undergo a relatively slight increase of thickness, and a 

 spindle-shaped thickening in the middle would still always 

 be possible. Mirbel, on the other hand, reckons as if all 

 the vascular bundles arrived at the base of the stem of 

 the same thickness as they are when they emerge from 

 the leaf, and comes to the conclusion, that in his stem 

 the mass of these fibres would form a cylinder, which in 

 the transverse section would display a surface nearly sixty- 

 four times larger than the cross section of the stem 

 actually was. To make a calculation of any use, it is ne- 

 cessary to settle the thickness of the lower end of the 

 fibres. I have before me the discoid slice of a full-grown 

 stem of Phoenix, 34 centimeters in diameter, in which 

 the fibres lying beneath the rind average 0*127, 

 therefore nearly | of a millimeter in diameter. Conse- 

 quently, if we assume with Mirbel that the upper 

 and middle portions of the fibres are 1 millimeter in 

 diameter, the cross section of about 64 of these fibres 

 would equal it. If, then, all the vascular bundles reached 

 the lower end of the stem under the form of such slender 

 fibres, taking the number of vascular bundles of MirbeFs 

 stem, the sum which he obtained must be diminished 

 sixty-four times, i. e. the mass of these fibres would form 

 a cylinder of the thickness of the Palm-stem Mirbel ex- 

 amined. I do not at all intend to attach any weight to 

 this calculation, its incorrectness is too evident, since, ac- 

 cording to it, the stem would consist of a compact fibrous 

 mass; but it shows that a calculation, if not based on 

 much safer grounds than Mirbel's rests on, cannot lead 

 to any useful conclusions. 



I admit unconditionally that my statement, that the 

 vascular bundles run down, in the form of fibres, to the 



