GERMINATION AND EMBRYOGENY OP GNETUM GNEMON. 289 



leaves. They are distinguished from the surrounding 

 tissue by ceasing to divide ; they soon attain an oblong 

 form (fig. 29) ; the terminal walls are at first transverse, 

 but as growth goes on they usually become oblique; the 

 ends of the component cells of the vessels thus assume a 

 similar relation to one another to that of the ends of the scler- 

 enchyma fibres. The protoplasm of the cells when young re- 

 sembles that of the surrounding tissue; but soon after the cells 

 assume the oblong form the formatipn of the latex begins. 

 Irregular masses of the substance similar to that contained 

 in the mature vessels appear in the protoplasm of the cells 

 (fig. 39) ; these increase in size as the development pro- 

 ceeds. 



In several cases more than one nucleus has been ob- 

 served in these cells (fig. 29), but this cannot be stated as 

 a constant character. Still it is a fact of interest when 

 connected with the development of the sclerenchyma fibres 

 above described. And it may be remarked that, were it 

 not for the early appearance of the latex in the young lati- 

 ciferous vessels, it would be almost impossible to distinguish 

 them from the young sclerenchyma.^ Even when mature 

 there is a close similarity between the two tissues in the 

 form of their component elements, as well as in the position 

 of those elements relatively to one another. 



No great importance is perhaps to be attached to the fact 

 that more than a single nucleus is found in some cases in 

 the cells which form the laticiferous vessels, but in this point 

 Gnetum Gnemon seems to differ from other plants having 

 articulated laticiferous tissue. 



In young laticiferous vessels are frequently to be seen 

 attached to the lateral walls small masses of a substance 

 which resembles the coagulum of latex in its properties, 

 but is distinguished from it by its position. It is possible 

 that these bodies may have some connection with the for- 

 mation of the sac-like outgrowths of the walls above de- 

 scribed, but this point has not been established. 



A similar substance is also found in comparatively large 

 masses on the walls which are about to be absorbed ; here, 

 as before, the proof that any constant connection exists 

 between the appearance of this substance and the breaking 

 down of the septum has not been obtained (fig. 30). 



^ A case like this appears as a strong excuse for the confusion of 

 sclerenchyma fibres with laticiferous tissue by Mirbel and others. Comp. 

 de Bary, ' Vergl. Anat.,' p. 20S. 



