DEVELOPMENT OF ARTICULATED LATICIFEROUS VESSELS. 141 



were on which the theory of cell-fusion was at this time 

 based is manifest from the fact that Hanstein still extends 

 this theory to the inarticulated latex-cells. 



Dippel's wory (1865), which also received a prize from 

 the Paris Academy, agrees with Hanstein's as regards the 

 main results. He finds that all laticiferous vessels consist 

 at first of cells arranged in rows, and those which do not 

 form a network are said by him to admit of being broken up 

 into their elements by means of maceration. Dippel, not 

 content with simply extending these results to the inarticu- 

 lated latex-tubes, claims to have actually seen the cross- 

 walls in these also. This statement has been refuted by 

 ])e Bary- and Schmalhausen, who have shown that the 

 cross-walls seen by him did not belong to the laticiferous 

 cells at all, but to other cells lying above or below them. 

 The same observers have also proved the incorrectness of his 

 conception of these vessels as modified sieve-tubes. 



Trecul published, between the years 1857 and 1868, a 

 long series of papers on the laticiferous vessels and allied 

 organs, which are remarkable for the great number of species 

 investigated. I will pass over his theory of circulation, 

 according to which the laticiferous vessels correspond to 

 the veins and the tracheae to the arteries of animals, and only 

 touch slightly on a few points, which are of interest with 

 reference to the development. 



Among the Papaveraceae Trecul ^ observed the origin of 

 these vessels from cells in Argemone. Here, as in other 

 cases, the latex is said to be formed before the cross-walls 

 are absorbed. And here, too, communication exists between 

 neighbouring vessels by means of protrusions, as is the case 

 with so many of the articulated latex vessels. 



Among the Cichoriacea3^ the development is described as 

 follows : — The laticiferous vessels arise from cells which are 

 fused into continuous tubes. The latter are all in com- 

 munication with one another, so as to form a network. The 

 communication between the cells comes about in three 

 different ways — 1. By the fusion of cells which stand one 

 above the other. 2. By the more or less frequent absorption 

 of the side walls at the points where two cells or vessels are 

 in immediate contact. 3. When the vessels are at a distance 



' As the work itself was not at my disposal, I had to use De Bary's 

 report in the ' Bot. Zeitung,' ISQT, p. '333, as well as references in the 

 ' Vergleichende Anatomic,' &c. 



* ' Vergleichende Auatomie,' p. 205. 



» 'Comptes Rendus,' t. 60, 1865, p. 522. 



4 Ibid, t. 61, 1865, p. 787. 



