APPENDIX. 53 



Meneghini has shown, on the contrary, that this condition 

 occurs in all Monocotyledons ; for the elucidation of this 

 he did not select Palms, but principally the stems of 

 Dractena, Aletris, and Yucca, in which, however, if his 

 theory be correct, the oblique course of the fibres de- 

 viates materially from that occurring in the Palms. In 

 order to give a review of the opinion promulgated by 

 Meneghini, an examination of his investigation of Dra- 

 caena and the allied forms is necessary. Meneghini states, 

 in regard to Dracana Draco, that no fibre of its stem runs 

 vertically, but that the upper part proceeds inward in the 

 direction of a radius, toward the centre of the stem ; near 

 this it turns downwards, and at the same time to the right 

 or left, and then runs obliquely downwards and outwards, 

 so that its inferior extremity lies beneath the surface of 

 the stem,, to the right or to the left of the upper end. 

 Perhaps no two vascular bundles of the same leaf exhibit 

 the same course, for some penetrate almost to the centre 

 of the stem before they turn downwards, others acquire a 

 curve at a short distance from the rind, some deviating to 

 the right, others to the left of the perpendicular line. 



The changes which the leaf undergoes during its deve- 

 lopment are regarded as the cause of this oblique course 

 of the fibres. As the adoption of this point of view by 

 Meneghini is wholly peculiar, and forms the most essential 

 part of his doctrine of the structure of the Monocotyledo- 

 nous stem, we must enter somewhat more minutely into it. 

 Meneghini assumes that, in all the Monocotyledons, the leaf 

 originates in the form of a closed, reversed funnel, which 

 subsequently becomes torn up along one side, either the 

 whole way or only at its upper part, by the pressure of the 

 younger leaves succeeding it in the interior. When only 

 the upper portion is torn, the lower part forms the sheath 

 of the leaf, and the leaf remains perfectly amplexicaul ; in 

 the other case, the relation of the base of the leaf to the 

 circumference of the stem does not necessarily remain 

 the same in its further development, but the stem usually 

 grows, proportionately, more in thickness, than the base 



