LATICI FERGUS VESSELS. 



189 



whether those coagula are really latex which came as such from the tubes, and not 

 products of coagulation of fluids which had diffused through the walls of the vessels. 

 Sect. 4'j. The distinctions of the two categories of laticiferous tubes depend upon 

 certain phenomena of their development and form. The articulated series, as types of 

 which those of the Cichoraceae, Papaveraceae, and Papayacese may serve, arise from 

 series of elongated cells of the meristem (or cambium), which coalesce, by perforation 

 of their septa, to form continuous tubes. In the simplest case, which occurs in Musa 

 and Chelidonium (Figs. 80, 81), the tubes remain simple, or are branched, and con- 

 nected in a net-work only inasmuch as one series of their original members may 







^i^:;J^^ 



Fig. So. — Chelidonium majus; tangential section through the 

 secondary cortex of an old root ; m — nt and b — b portions of milk* 

 tubes between the cells of the parenchyma. At a — a m passes 

 beneath the parenchymatous cells {225). 



Fig. 81. — Chelidonium majus; stem, cortex, radial 

 section, part of a milk-tube with a perforated sep- 

 tum at s (225). 



continue its course from any given point as two diverging series, and conversely. 

 The septa between the original members are here perforated only in the middle by 

 one or few holes ; their margin is persistent ; occasional large openings in the lateral 

 wall also occur in rare cases, where two tubes are directly contiguous. 



In the majority of really typical cases the septa between the members of each 

 series soon disappear completely, so that in the mature tube no trace of them re- 

 mains. Occasionally in such cases single septa may persist through life. 



The tube puts out lateral protrusions, usually at numerous points, which force 



