vessels, at this period, are with difficulty recognized from elongated 

 cellular tissue, except from their very attenuated form, their ends be- 

 ing more pointed and containing a single cytoblast, much larger and 

 more elliptical than that of any cell of the surrounding tissue.* In 

 the bulb of Scilla maritima the young vessels appear at first under 

 the form of a cell shaped as if composed of two very acute cones 

 applied end to end, there being scarcely any cylindrical portion be- 

 tween them. As development proceeds the vessels rapidly increase in 

 length till they arrive at perfection, but not so in diameter, for the di- 

 mensions in that direction are attained almost from the first formation. 



At this period, in the living plant the young vessels appear full of 

 fluid, which is apparently, as Schleiden remarks, of a thick character, 

 and which he has designated vegetable jelly ; but if boiling have been 

 employed or alcohol added, the contents, or at least the albuminous 

 portion, become coagulated, and every cell appears from this circum- 

 stance to contain another within it in a shrivelled condition ; which 

 appearance did not exist before the application of heat or of alcohol, 

 and occasionally the shrivelling goes to the extent that all that can 

 be seen of the contents is a thick granular cord extending down the 

 vessel. 



From these observations it is evident that the membranous tube of 

 a vessel is formed on the same plan as the same part is in ordinary 

 cells, and which act is entirely perfected before the commencement 

 of the formation of the fibre within. And the occurrence of the cyto- 

 blast, and only one in each vessel, clearly demonstrates that the ends 

 of several superimposed cells have not been absorbed to make one 

 tube of greater length ; if so, we should perceive as many cytoblasts 

 as there had been cells so appropriated : but the fact is the reverse ; 

 one only is found, and that of large size, bearing the same proportion 

 to the dimensions of the vessel as every cytoblast does to its own cell. 



As long as the cytoblast exists, the commencement of the deposi- 

 tion of the fibre within cannot be observed, which fact, Schleiden 

 mentions, takes place also in cells ; in reality the vessel is not yet deve- 

 loped, and the fibre is only deposited when the contents assume a 

 change that is observed after the disappearance of the cytoblast ; but 

 occasionally I have observed the commencement of the formation of 

 the fibre whilst the cytoblast exists. 



When this body has disappeared, the membranous tube of the ves- 

 sel has by this time approached very nearly its perfect size, and I 



* In this state they may be taken for ducts of the latex, and I have more than 

 once seen circulation in them. 



