TERMINOLOGY OF THE VASCULAR BUNDLES. 401 



rather as a central cylinder or plerome-strand differentiated into tracheal plates, phloem 

 strands, pericambium, &c. But this method, if consistently carried out, must lead at 

 once to that general breaking-up of the vascular bundle, which, as already stated above, 

 though completely justified in principle, is certainly not desirable in the interests of clear 

 description. 



With reference, secondly, to the Jermhiology employed, I have, as will be granted, aimed 

 at the greatest possible simplicity and clearness of expression, and endeavoured, as far as 

 possible, to preserve or to restore names of long standing. I must apologize for the 

 single really new word, Epithema ; it is not pretty, but I could not find a better one. 

 The reasons for keeping or not keeping most of the names which come into question follow 

 partly from what has just been said, partly from the necessity of being consistent in expo- 

 sition, while they have in part been expressly stated in the latter. It would lead us too 

 far, and would not be interesting, to discuss them all severally in this place. My motive for 

 substituting the old expression vascular bundle for the term fibro-vascular bundle, which 

 has lately become more usual, has likewise been generally stated above, partly at pp. 232 

 and 318, partly in the earlier portion of this note. In fact vascular bundle, in the above 

 description, denotes something diff"erent from Niigeli's expression Fibro-vascular strand, 

 inasmuch as the latter comprehends the accompanying fibrous tissue, which has been ex- 

 cluded from the vascular bundle above. A vascular bundle may appear as an essential 

 part of a fibro-vascular strand, but it is not necessarily, and very often not actually com- 

 bined with accompanying fibrous tissue, and the two things must therefore be dis- 

 tinguished. I have preferred the expression vascular bundle to the more recent 

 ' conducting bundle,' because it is the traditional term, which is also preserved in the 

 phrase fibro-vascular strand, and because no decisive ground appears to me to exist for 

 laying aside the old convenient word, which correctly indicates the principal point, or 

 for limiting its application. 



Caspary' has adopted the latter course, and has distinguished the bundles containing 

 tracheides, under the name of 'cellular conducting-bundles,' from those which contain 

 vessels, and comprehended both under the name conduct ing-bundle, because he assumed 

 a great difference between tracheides and vessels, like that between cells and vessels. 

 As the distinction between the two forms of organs is actually a very trifling one, the 

 ground for the sharp severance of the two kinds of bundle, and thus for the change of 

 name, in my opinion disappears. It is no doubt an inaccuracy which is permissible in 

 the interests of simplicity of expression, to speak of vascular bundles without vessels, i. e. 

 bundles in which the latter are replaced by tracheides. 



' Berliner Acad. Monatsber. 10 July, 1S62, p. 453. 



Dd 



