DEVELOPMENT OF ARTICULATED LATICIFEROUS VESSELS. 147 



that the first indications of the absorption of the cross- 

 walls are usually to be observed. At this stage of develop- 

 ment the condition of these vessels is as follows : 



In the root the hypodermal vessels are already in a fairly 

 advanced state ; they contain latex, and here and there it 

 can be seen that the cross-walls are perforated, at any rate 

 in the middle. The other system, that which belongs to 

 the axial cylinder, is more backward in its development. 

 The contents of the cells are not visibly different from those 

 of the other procambial cells ; and all their walls are still 

 unaltered. 



The same conditions prevail to a certain extent in the 

 hypocotyl. Here, however, the development of the two 

 systems is more nearly equal. 



At the base of the cotyledons the connecting branches 

 between the axial and the hypodermal latex-vessels are as 

 far advanced as the main trunks themselves. They already 

 contain some latex. In this region one occasionally finds 

 cross-walls which are already perforated. In the upper part 

 of the cotyledons the development is not so far advanced. 

 The cross-walls are everywhere present, though sometimes 

 slightly swollen. Towards the apex of the cotyledons no 

 latex can be detected in the vessels. 



The laticiferous vessels in the cotyledons already form a 

 complex network. The connection between the main trunk 

 is always formed by cross rows of cells, which afterwards 

 undergo fusion. In these germ plants I have never observed 

 union by conjugating outgrowths, which is so common else- 

 where. 



Cases not unfrequently occur in which one or more cells 

 of a row are divided into two by longitudinal walls. Both 

 the cells so formed take part in the formation of the vessel. 

 Here a subsequent bi-partition has evidently taken place in 

 some of the cells which already constitute the young latex- 

 vessel, while the other cells remain undivided as usual. 



In germ plants, where the root has attained a length of 

 about six mm., all stages in the development of the latici- 

 ferous vessels can be observed. I will follow the same order 

 as before, and begin with the hypodermal vessels of the 

 root. These are now almost in the mature state. The 

 cross-walls are all perforated, and it is sometimes difficult 

 to find any traces of them. The articulations are very long, 

 generally twice as long as the parenchyma cells, which are 

 themselves much elongated. Thus the same relative length 

 is still maintained as exists in the earliest stages of develop- 

 ment. The laticiferous vessels of the axial cylinder, on the 



