APPENDIX. 79 



of some two inches. About six leaves on this had no 

 amplexicaul vaginas, but the lower sheath-like portion of 

 all the leaves formed a connected lamella, passing round 

 the stem in a spiral line, from the upper part of which 

 normally -formed leaves were given off at intervals. The 

 upper leaves had perfectly closed sheaths. Similar con- 

 fluence of several leaves into a continuous leaf-spiral have, 

 as is well known, been repeatedly observed in plants with 

 verticillate leaves, ex. gr. in Casuarina, whether they have 

 elsewhere occurred in amplexicaul leaves I know not ; in 

 any case, the case just described appears to me incon- 

 sistent with the idea of the origin of the leaves in the 

 form of closed vesicles. 



The development of the originally simple leaf into a 

 pinnate leaf is very peculiar in the Palms. Since Mirbel 

 rather indicates than describes this process, a more minute 

 explanation of it will, though not very closely connected 

 with the object of this essay, perhaps be acceptable to 

 many readers. De Candolle, in his ' Organography ' 

 (i, 304), has already observed, that the division of the 

 Palm-leaf into pinnae, or into lobes of a fan-shaped leaf, 

 takes place in a manner altogether peculiar, namely, by 

 a tearing up of the structure. De Candolle looked at this 

 process much too roughly ; he evidently made his ob- 

 servations on a leaf already developed to a considerable 

 degree ; I was therefore quite justified in rejecting this 

 notion of a mechanical description in my ' Anatomy of 

 the Palms/ but in like manner did not go far enough 

 back in the investigation of the young leaf, in its earliest 

 stages of development, to enable me to give a satisfactory 

 explanation of the process. I had indeed correctly made 

 out that the separation of the pinnae is completed long- 

 before the unfolding of the leaf, and that they are not 

 connected together in the bud by leaf -tissue, but by a 

 loose parenchyma, which is blended in a very narrow line 

 with the border of the leaf, is connected with the pubes- 

 cence of the leaf, and dries up and falls off with it, 

 whereby the leaflets are allowed to separate from each 



