CONDUCTING TISSUES OF FUNGI 391 



Whether the " sieve-tubes " of Ehodophyceae and Phaeopiiygeae serve 

 to transport synthetic products other than protein-compounds, or 

 whether special conducting elements are provided for that purpose, is 

 a matter for further investigation. 



In the relatively complex rhizomorphs of certain Fungi (Phallaceae, 

 Lycoperdaceae, some Agapjcineae), those longitudinal " medullary " 

 hyphae which are not mechanical in character, probably act as organs 

 of translocation. In some Hymenomycetes especially Agaricus praecox, 

 A. olearius, and other Agapjcineae the fleshy fruit-bodies contain 

 certain long tubular hyphae filled with a dense and often highly refractive 

 substance, which upon closer investigation may prove to be conducting 

 elements. The fruit-bodies of Lactarius are furnished with [genuine] latex- 

 tubes, in the shape of wide hyphae, with soft extensible walls ; the 

 finely granular latex contained in these tubes exudes from wounded 

 surfaces in viscid drops, and coagulates on heating or upon treatment 

 with alcohol. It is quite likely that the function of these latex-tubes 

 is similar to that of the synonymous organs of Phanerogams, or, in other 

 words, that they are concerned with the translocation of plastic 

 substances. Morphologically considered, the laticiferous elements of 

 Lactarius deliciosus and probably of other species of Lactarius as well 

 correspond, according to A. Weiss, to articulated tubes (latex-vessels), 

 since they are formed from rows of cells in which the transverse walls 

 become obliterated. The fruit-bodies of Lactarius also contain 

 specialised hyphae of a different kind. These latter are narrow and 

 thin-walled, and are filled with clear liquid contents ; they are 

 surrounded by relatively large parenchymatous cells, which exhibit a 

 rosette-like arrangement in transverse sections. It is uncertain whether 

 these hyphae are also engaged in the transportation of plastic materials, 

 or whether they possibly act as water-conducting channels. 



VI ONTOGENY OF THE CONDUCTING SYSTEM. 



Most vascular bundles are derived from primary procambial strands. 

 In special cases, however, small bundles may be differentiated from 

 fundamental meristem through the agency of secondary procambial 

 strands ; in the haulms of Papyrus antiquorum, for example, the small 

 cross-connections in the diaphragms are formed in this way. The 

 primary conducting parenchyma, comprising the parenchymatous bundle- 

 sheaths and " nerve-parenchyma " of the leaf, and the medullary, cortical 

 and interfascicular (medullary ray) parenchyma of the stem, but exclud- 

 ing the parenchymatous elements of the hadrome and leptome, arises 

 out of the fundamental meristem. 



The ontogenetic origin of the endodermis 182 is quite as variable as its 



