182 Mr. A. Henfrey on some Points in the St7-ucture 



stems, of which I shall have presently to speak ; before passing 

 to these, however, I must refer to the controversies which exist 

 as to the course of development, in time, of the different portions 

 of the fibro-vascular bundles. Von Mohl offers, I believe, no 

 opinion on this point ; Schleiden states that their development 

 commences below and extends upwards into the leaf, in which 

 opinion he is borne out by the statements of several authors, 

 particularly Mirbel* and Naudinf. Gaudichaud J states that 

 the development begins in the centre, and that an ascending and 

 a descending portion are gradually organized, one passing to the 

 leaf, the other to the roots. 



My own observations are in favour of the former opinion, and 

 indeed Gaudichaud's publications are wanting in proper scientific 

 completeness. His statements are much too dogmatic, and his 

 figures have too much of the character of diagrams, to be re- 

 ceived as direct evidence in a case where such complex structures 

 are in question. 



In the very youngest part of the bud the nascent leaf is 

 wholly cellular ; the cells have generally a spherical form, like 

 those of the other organs and of the conical summit of the stem ; 

 the whole are clothed by a delicate epithelium. But in the sub- 

 stance of the stem and nascent leaves are to be remarked certain 

 regions, where the cells, in the earliest condition I have seen 

 them, have a peculiar appearance, being elongated and arranged 

 in parallel rows (PI. X. fig. 1 a, a) ; in the centre of these bun- 

 dles of elongated cells first appear the vessels, which are at first 

 unreliable spiral vessels ; these regions are in fact the nascent 

 fibro-vascular bundles. These fibro-vascular bundles appeared 

 to me to be always younger and less perfect as they approached 

 the apex, or punctum vegetationis. The further development of 

 these elements into the ducts and woody structures found in full- 

 grown bundles I have not systematically followed, as I was more 

 particularly anxious to attain a clear view of their anatomical 

 relation to each other and to the roots. 



The condition of the relations of the bundles above indicated is 

 the same as that which exists in most bulbs, and is the form which 

 gives the type characterized by Schleiden as consisting of a stem 

 where the internodial portions are little or not at all developed. 

 I believe that the stem of a solid Palm has essentially the same 

 relative arrangement of the parts. The other type is found in 

 some Palms and in the annual stems of Grasses; this is charac- 

 terized by the development of the internodes. 



In regard to the flowering-stem of the first form we have two 

 modifications to discriminate, depending on the position of the 



* Ann. des Sc. Nat. 2 ser. xx. 6. f Ibid. 3 ser. i. 162. 



X Recbercbes gen. sur l'Organographie, &c. Paris, 1841. 



