APPENDIX. 85 



of the bud, before they appear in the leaves, and that, 

 subsequently, the origin of the vessels in these rudimentary 

 vascular bundles follows in the same direction. This 

 result has been fully confirmed by the researches of 

 Schleiden (Grundziige, ii, 189), Meneghini (Intorno alia 

 struttura del tronco delle Monocotiledoni, in Miscellanee 

 di Chimica, Fisica e Storia naturale, 1843), and Naudin 

 (Ann. des Sc. nat., 1844, i, 162); and after these ac- 

 cordant observations, there can be no doubt that the 

 upper end of the vascular bundle grows from below up- 

 ward, and that we have to seek its origin in the stem, 

 and not in the leaf. But it is quite a different question, 

 whether this process of development occurs throughout 

 the whole of the vascular bundle, or if its lower end, 

 running downward in the stem, grows in the opposite 

 direction. Mirbel assumes the former, and assures us that 

 in the Palms, the same vascular bundle has already, at its 

 lower end springing from the interior of the periphery of 

 the stem, the characters of developed wood, and exhibits 

 in its intermediate parts, the half-solidified condition of 

 the alburnum, while at its upper extremity it consists of 

 nascent tissue. Has Mirbel really observed this ? I here 

 take the liberty to doubt. According to my own observa- 

 tions, the vascular bundle of a Palm, the lower end of 

 which already exhibits a ligneous solidity, goes, not to the 

 rudiment of a leaf, but to one already tolerably advanced 

 in development ; therefore, if the portion of it lying in 

 the upper part of the stem be still very soft, from the 

 causes explained above, this can give no further result 

 as to the mode of its first production. We can only ar- 

 rive safely at such by tracing downwards one of these 

 vascular bundles, the upper part of which has not yet 

 reached a leaf, and observing its further gradual develop- 

 ment. From the great number and the entangled con- 

 dition of the vascular bundles, I was unable to do this in 

 a Palm-stem, and my efforts to make out this point by 

 direct observation totally failed. When, in spite of this, 

 I venture to discuss the question, and to deduce a decision 



