LATICIFEROUS TISSUES OF PLANTS 45 



yield gutta percha, Palaquium spp. of the natural order 

 Sapotaceae. 



A full knowledge of the nature of the laticiferous tissue 

 in the different rubber-yielding plants and of its distribu- 

 tion and the mode of its formation in the cortex of the 

 tappable trees would probably be of great assistance in 

 devising methods of tapping suited to the peculiarities of 

 the various species, but at present the information avail- 

 able on this subject is somewhat limited. The principal 

 investigations of the laticiferous tissues of rubber-yielding 

 jilants have been conducted with Hevea brasiliensis and 

 Manihot Glaziovii, and have been largely confined to the 

 seedlings of these plants. 



Scott * first demonstrated in 1885 that the laticiferous 

 tissue of Hevea brasiliensis seedlings consisted of articu- 

 lated vessels formed from a number of separate cells. 

 Working with seedlings up to thirty-six days old, he found 

 that well-developed laticiferous vessels, containing abun- 

 dant latex, were present in the cotyledons of the germin- 

 ating seeds, and that these vessels were always produced 

 on the phloem side of the bundles. The transverse walls 

 of the original cells could be easily traced in different 

 stages of absorption, and even at this early period numerous 

 perforations of the lateral walls had occurred, thus estab- 

 lishing communication between adjacent vessels and 

 producing a complete anastomosing system of laticiferous 

 tubes. He further found that the cortex of the seedlings 

 contained a similar network of laticiferous vessels which 

 could be traced up to the youngest leaf at the apex of 

 the stem but not into the apical cone. 



Miss Calvert f subsequently found that a small number 

 of laticiferous vessels also occur in the pith of Hevea 

 seedlings, and that the vessels of the pith and cortex com- 

 municate with one another at the nodes. 



Fitting i has since confirmed the conclusions of Scott 

 and Miss Calvert regarding the distribution of the latici- 

 ferous vessels in Hevea seedlings, and has also examined 

 trees from one to three years old. In the latter he found 

 a number of laticiferous vessels in the outer part of the 

 pith and showed that these were mutually connected. 



* Journal of Linnean Society, xxi. pp. 566-70. 



t Annals of Botany, i. pp. 75-7. 



% Beihefte zum Tropenpflanzer, 1909. 



