138 D. H. SCOTT. 



laticiferous vessels are composed. In other respects, how- 

 ever, his theory was directly at variance with the facts. 

 The fact especially that all laticiferous vessels, both the 

 articulated and the inarticulated, form continuous open 

 tubes which may traverse the whole plant, was ignored, and, 

 indeed, expressly denied by Schacht, who asserts that these 

 '' bast-cells " are never connected with one another. Thus, 

 not only the development but even the anatomy was com- 

 pletely misunderstood. 



In 1855, linger ^ came forward again as the representa- 

 tive of the cell-fusion theory. In the work cited all latici- 

 ferous vessels are described under the heading cell-fusions. 

 The author expresses his view as follows : — " As the result 

 of many researches, carried out according to this method,'^ it 

 has been established that the elements of the laticiferous 

 vessels are always cells of peculiar fluid contents. These 

 cells appear as short or long, simple or repeatedly branched 

 cylindrical sacs, the ends and branches of which frequently 

 inosculate, so that a system of communicating tubes proceeds 

 from them." The mode of development is not described 

 more in detail ; Unger had probably traced it only in the 

 case of some plants with really articulated laticiferous 

 vessels, such as Chelidonium and Sanguinaria,^ and then 

 assumed that the results of his researches also applied to 

 the inarticulated latex-cells, an error which is the more 

 excusable as the distinction between the two categories of 

 laticiferous canals had not yet been detected. 



In 1856, the first minute investigations of the develop- 

 ment of articulated laticiferous vessels were published by 

 Schacht,^ who, however, only actually traced the process in 

 one plant, Carica pcqKiya, The remarkable latex vessels 

 of this genus form, as is well known, a much branched 

 system, which here, unlike most other cases, is developed on 

 the inner side of the cambium. They form concentric 

 circles in the xylem, tracheae and laticiferous vessels 

 being produced alternately by the cambial layer. The 

 cross-walls and also portions of the side-walls are, according 

 to Schacht, soon absorbed. The main trunks of the vessels 

 also send out numerous branches, which are sometimes 

 extremely thin, and these can either inosculate with other 



' • Anatomie und Physiologic der Pflanzen,' p. 157. 



- Maceration and boiling with potash. 



^ The latex- sacs of Sauguinaria are not in communication, and are, 

 therefore, of course no longer reckoned among laticiferous vessels ; but 

 this was not known in Unger's time. 



* ' Monatsberichte der Berliner Akademie,' 1S56, 2, p. 615. 



