112 Rev. J. B. Rcade on I he Erist Cure of S/jiral Vessels 



main trunk and leal-stalks of the carrot led to an examination 

 of the layer of vessels which lie immediately under the bark 

 of the root, and these I found, at first si ght, to have every ap- 

 pearance of closely-wound tracheae. Their brittleness, how- 

 ever, and the frequent anastomosis of the successive coils in- 

 duced me to suppose that they were annular and not spiral; 

 but, upon maceration, the strong membranous tube to which 

 the fibre was firmly attached suffered speedy decomposition, 

 and the spiral thread was readily unrolled. These tubes taper 

 off at each extremity into conical terminations, and I have 

 seen the contained fluid pass from tube to tube through the 

 oval perforation where they overlap each other. This pecu- 

 liarity of structure, I am well aware, may be looked upon as 

 imparting to these vessels an intermediate form between elon- 

 gated cells and true vascular tissue ; and hence, perhaps, I 

 ought not to adduce them as examples of the true spiral. I 

 would however notice the curious fact that all the very nume- 

 rous vessels in this root are of the kind now described. Such 

 is not the case in the root of any other dicotyledon which I 

 have hitherto examined. 



In the paper to which 1 have referred I rested the fact of 

 the occurrence of spiral vessels in the roots of dicotyledonous 

 plants upon the single example of the root of common garden 

 mint. To this I may now add the roots of the radish, dahlia, 

 Convolvulus minor, and mustard. The interesting phaenomena 

 connected with the development of the root of mustard, as well 

 as the structure of the root itself, will amply repay the most 

 minute attention. If a seed be immersed in water, the testa, 

 in the course of a few hours, will be covered with very minute 

 vessels, starting like radii from its surface. The peculiar re- 

 fractive power of these vessels renders them a remarkably dif- 

 ficult microscopic object, and I should probably have failed 

 without the assistance of my friend Mr. Bowerbank in ar- 

 riving at an accurate knowledge of their structure. Their 

 form is entirely novel. A number of wine glasses, with long 

 stems, and inserted into each other, may furnish a somewhat 

 apt illustration of their remarkable appearance ; and as the 

 walls of the bell-shaped portion are strengthened by a spiral 

 fibre, the vessels may be described in one word as fibro-cam- 



