DEVELOPMENT or ARTICULATED LATICIFEROUS VESSELS. 151 



just like those in the germ plants except that the young 

 latex-vessels formed from the cambium are rather larger. 



The laticiferous vessels of the secondary cortex are also 

 very well developed in the root of Taraxacimi officinale. 

 Looked at in cross-section they are ranged in a number of 

 concentric circles, which alternate with thick layers of paren- 

 chyma, and are broken by the cortical rays. Within each 

 of these circular bands the latex-vessels form groups of in- 

 definite size. They are very narrow, and have a rather 

 crooked course. They are accompanied by small sieve- 

 tubes. The cells from which the latex-vessels are developed 

 have wedge-shaped ends, with the surfaces inclined to the 

 radial plane. Accordingly the perforations are best seen in 

 tangential section. The form and course of the vessels 

 correspond exactly with those of the cells from which they 

 are produced. In successful preparations one can establish 

 that in the immediate neighbourhood of the cambium the 

 cross-walls are still present. 



In Chelidonimn majus the origin of the laticiferous vessels 

 from cells is so unmistakeable, even in the mature state, that 

 an investigation of the development seems, from this point 

 of view, superfluous. A few points, however, came before 

 me in the course of my observations, which it may be worth 

 while to mention. 



In the secondary cortex of old roots the very numerous 

 latex-vessels are irregularly distributed in the parenchyma. 

 Sometimes they are isolated, sometimes two or three are in 

 contact. Sieve-tubes are also present, and these, too, are 

 here and there in actual contact with the laticiferous vessels. 

 In the root the articulations are very short, about three times 

 as long as they are broad. In the stem and leaves they are 

 very long. Neither outgrowths nor other ramifications 

 occur. Where, however, two vessels are in contact, the 

 side-walls are often perforated. In the cross-walls the per- 

 forations generally remain very small, so small that it often 

 requires careful focussing to detect them. Accordingly the 

 contents of two successive articulations are not in very close 

 connection. In alcohol material the continuity is generally 

 already interrupted owing to contraction ; and on solution of 

 the cell-walls with strong sulphuric acid the contents do 

 not remain behind as a continuous cord (as always happens 

 in the Cichoriacese), but break up into a number of frag- 

 ments corresponding to the constituent cells. The per- 

 forated cross-Malls often have remarkable thickened ridges, 

 with a circular section (fig. 9). 



The contents of these vessels are comparatively trans- 



