44 THE PALM-STEM. 



vascular bundles, but some of them are met with scattered among the vas- 

 cular bundles of the stem, for example, in Astrocaryum vulgare, Cocos botry- 

 ophora, coronata, Leopoldinia pulchra. I have met with this modification 

 principally in the Cocos-\\ke, stems, in others only in rare cases. These 

 fibres, therefore, only occur in such stems as possess a fibrous layer abun- 

 dantly furnished with fibres, and a great many vascular bundles. Consequently 

 it is probable, that in the great mass of closely-crowded bundles which fill 

 up these stems, circumstances readily arise, which prevent the nascent fibres 

 from becoming developed in the normal positions, and give rise to their 

 origin in unusual places. These scattered fibres, too, do not seem to occur 

 in all specimens of the same species, at least they were very abundant in one 

 stem of Leopoldinia pulchra, while in a second they were altogether wanting, 

 which evidently proves that accidental causes give occasion to their origin. 



3. Mirbel fell into still greater error than Moldenhawer in his researches 

 into the course of development of the vascular bundles of the Monocotyledons. 

 He states (Annal. du Museum, xiii, 69) that each vascular bundle is formed, 

 at its origin, solely of one bundle of large ducts (reticulated vessels), that 

 around these a tissue of delicate tubes is gradually formed, by which is un- 

 derstood the cellular tissue of the wood, the spiral vessels, annular vessels, 

 the proper vessels, and the liber-bundle, these parts not being distinguished. 

 The membrane of these tubes, then, gradually becomes so much thickened 

 that at length their cavities are filled up. 



4. In a description of the vascular bundle of Calamus (Ann. d. Sc. nat. ii, 

 pp. 229-236), Amici attributes a different import to the different parts of 

 the vascular bundle from that which I have done. Amici considers the 

 wood-cells to be liber-tubes, the liber-tubes proper vessels, the proper 

 vessels he indeed recognises as thin-walled and not porous tubes, but leaves 

 it undetermined to what kind of organ they belong. The description and 

 representation of the vascular bundles of Calamus, given by Kieser (Phytot. 

 p. 121, Tab. iii, fig. 29), deviates still more from the truth, since the liber- 

 and wood-layers are not distinguished at all, and the proper vessels are 

 regarded as spiral vessels. 



5. I shall readily be excused from detailing minutely the views of 

 Lestiboudois ; he believes that the Palm-stem is to be compared with the 

 bark of the Dicotyledons, he finds nothing analogous to wood and pith. 

 (Principes de Botanique, pp. 149-158.) This strikingly testifies how little 

 he is acquainted with the minute anatomy of plants. 



