340 



CONDUCTING SYSTEM 



that the functions of the two sets of organs are similar, an impression 

 which is strengthened by a consideration of the chemical composition of 

 latex. The anatomical relations, finally, which exist between the 

 laticiferons and photosynthetic systems render it still more probable 

 that latex-tubes play a considerable part in the translocation of carbo- 

 hydrate materials at any rate. The author's observations with regard to 



this point which have been confirmed and 

 largely extended by Pirotta and Marcatili, and 

 independently by Gaucher may be sum- 

 marised as follows. In foliage leaves the 

 latex-tubes ramify most abundantly immediately 

 beneath the palisade-layers which represent 

 the special photosynthetic tissue. Not infre- 

 quently, individual branches of the laticiferous 

 system depart from the main trunks that 

 accompany the vascular bundles, turn upwards 

 (Fig. 138) and insinuate themselves between 

 the palisade-cells, where they are in a position 

 to receive the synthetic products at first hand. 

 The ultimate branches of latex-tubes often act 

 as the points of attachment for converging 

 groups of palisade-cells (Uujjhoriia spp., Ficus 

 nitida, Hypochaeris radicata) ; where this direct 

 contact is not feasible, funnel-shaped collecting- 

 cells are interpolated, which effect the trans- 

 ference of synthetic products from the palisade- 

 cells to the latex-tubes (Fig. 138 b). Such 

 cases at once recall the previously described 

 arrangements for linking up the photosyn- 

 thetic system with the efferent parenchymatous 

 bundle-sheaths, which are found in the foliar 

 organs of plants that do not possess latex-tubes. 

 Certain tissue-correlations also suggest that latex-tubes are con- 

 cerned with the conduction of plastic materials. Thus the degree of 

 development of the laticiferous network in a leaf is found to be inversely 

 proportional to that of the conducting parenchyma. Where the latici- 

 ferous system is abundantly developed in the mesophyll, it relieves the 

 foliar conducting parenchyma and particularly the bundle-sheaths to 

 a large extent of the office of translocation ; in these circumstances, the 

 normal efferent tissues exhibit a comparatively slight and imperfect 

 organisation. This reduction of the conducting parenchyma in the 

 presence of a laticiferous system is very strikingly illustrated, accord- 

 ing to the author's observations, by Eiupliorhia Myrsmitcs and E. 



Fig. 138. 



Relations of latex-tubes to the 

 photosynthetic tissues in various 

 leaves. A. Euphorbia Myrsinites 

 (exceptional ease). xlTO. B. E. 

 biglandulosa ; a, collecting cells ; 

 m, latex-tube. X210. C. Hypo- 

 chaeris radicata. XlTO. (For ex- 

 planation see text.) 



