288 F. O. BOWER. 



mature these overlap one another at their ends, so as to 

 form a continuous system. If such fibres in early stages of 

 their development be examined, they are found to have two 

 or more nuclei ; the larger the number of the nuclei the 

 less definite is their outline (fig. 26). Similar fibres occur 

 in the petiole and lamina ; in the latter they branch, and 

 form a dense mat, permeating the intercellular spaces of the 

 leaf immediately beneath the epidermis. 



Laticiferous vessels. 



In the parenchyma of the stem and leaves of G. Gnemon 

 (but not observed in the root) are to be found laticiferous 

 vessels, which appear when mature as tubes of considerable 

 calibre, with cellulose wallsj and contents having the 

 characters of latex. The walls are smooth and of medium 

 thickness ; where two members of the vessel are contiguous 

 at their oblique ends (fig. 27) the wall is more or less com- 

 pletely absorbed, and the contents of the originally separate 

 cells are connected with one another. 



On the lateral walls are found not uncommonly points 

 where the wall is thin, and has bulged outwards as sac-like 

 protuberances, which encroach upon the cavity of neigh- 

 bouring cells ; these thinner points in the walls are pitted 

 (fig. 28), but not perforated (de Bary, ' Vergl. Anat.,' 

 p. 195). 



The latex, when coagulated with alcohol, appears under 

 the microscope as an amorphous, highly refractive, yellow- 

 ish substance. It swells with potash, but resumes its 

 original appearance on acidulating. It stains a deep yellow 

 with iodine or Schultze^s solution ; it resists strong sul- 

 phuric acid, retaining its sharp outline, and turns a dusky 

 black after treatment with osmic acid. Highly refractive 

 globular bodies, which give similar reactions, occur in the 

 cells of the surrounding parenchyma. 



It appears, then, that we have to deal with a latex of 

 similar character to that of the Angiosperms. 



The laticiferous vessels appear at a very early stage in 

 the young seedling, and may be recognised while the feeder 

 is still very small. Their development is, however, more 

 easily traced in longitudinal sections of the bud of the older 

 plant, and the following results are in the main obtained 

 from this source. 



The laticiferous vessels are derived from cells which are 

 arranged with considerable regularity in longitudinal 

 rows ; such cells are to be found in the young stem and 

 leaves, but not in the apical cone above the youngest 



