LATICIFEROUS TISSUE OP HEVEA SPRUOEANA. 206 



Note on the Laticiferous Tissue of Hevea 

 spruceana. 



By 



]>. H. Scott, M.A., Pfa.D. 



(From the Jodrell Laboratory, Kew.) 



The genus Hevea belongs to the sub-tribe Jatropheae (Tribe 

 Crotonese, N. O. EuphorbiaceEe), according to the classification 

 adopted in Bentham and Hooker's Genera Plantarum. I was 

 not able to obtain material of the most important commercial 

 species, H. brasiliensis, the Para rubber, as none could be 

 spared just now from the Kew collection, but it is not probable 

 that important differences exist between this species and H. 

 spruceana, as regards the subject before us. 



In the stem of the latter plant the general distribution of 

 the laticiferous tissue is similar to that in Mauihot. There is 

 a somewhat scanty system of laticiferous tubes in the outer 

 cortex, Avhile within the bundle-sheath, which here also is 

 "compound," consisting of sclerenchyraatous fibres and scle- 

 rotic cells, the tubes are very abundant. They occur with 

 equal frequency in the primary and in the secondary phloem ; 

 the latter is here formed in considerable quantity. 



In the petiole also laticiferous tissue is present both in the 

 phloem of the bundles and in the external parenchyma. 



In the polyarch (adventitious) roots, the laticiferous tubes 

 are confined to the phloem groups, and have not been found in 

 the outer cortex. 



Tangential sections through any of the regions in which the 

 laticiferous tubes occur, show that the latter form a complex 

 anastomosing network. 



