428 CONSERVATIVE ORGANS. [LECT. VIII. 



spirals ; in the third internodial space they are still 

 larger, and two or three of them have become 

 punctuated spirals ; and the number of these in- 

 creases as we descend in the examination of the 

 stem. In the mature stem, near the centre, each 

 fasciculus contains six large punctuated spirals, and 

 near the root only six of the twenty-nine vessels in 

 each fasciculus are simple spirals, all the rest being 

 punctuated. The same phytologist also asserts, 

 that as these vessels enlarge, their sides become 

 thicker and more opaque, and a sort of cellular 

 tissue is formed within them *. A similar variety 

 in the number of the vessels which compose the 

 fasciculi of sap vessels, occurs in almost all her- 

 baceous plants ; and my observations tend, also, 

 to confirm Kieser's remarks respecting their aug- 

 mentation in size ; but I have not been able to 

 satisfy myself of the correctness of his opinion, 

 that the transformation of the simple spiral vessels 

 is the cause of the diversity of character of the 

 vessels in the different parts of the stem. I 

 have not examined the Gourd ; but in the stems 

 of Bryony and of the Cucumber, which belong 

 to the same natural order of plants, I have found 

 the three distinct kinds of sap vessels, which 

 I demonstrated to you in our examination of the 

 structure of the stem of Bryony, in every part of 



'* Mem. sur I' Organisation des Planles, p. 134-. 



