DIV. I 



MORPHOLOGY 



69 



resin), caoutchouc, gutta-percha, fats and wax occur, and as a solid constituent 

 proteid granules. 



The laticiferous tubes in Euphorbiaceae, Moraceae, Apocynaceae, 

 and Asclepiadaceae proceed from cells 

 which are already recognisable in the 

 embryonic plant, and with the 'growth of 

 the latter continue to grow, branch, and 

 penetrate all the organs so that they may 

 become many metres in length. 



(2) CELL-FUSIONS. A number of 

 secretory cells may unite to form a more 

 spacious reservoir for the secretion, by the 

 dissolution of the waflls between them. 

 This is most strikingly seen in the LATICI- 

 FEROUS VESSELS. They resemble the latici- 

 ferous cells in appearance and in their 

 contents, but differ in their origin by the 

 fusion of a number of cells forming a net- 

 work (Fig. 73). Eemains of the trans- 

 verse walls may be recognised in this. 



The laticiferous vessels, like the lati- 

 ciferous cells, are limited to certain families 

 of plants, for instance the Papaveraceae 

 (Papaver, Ghelidonium, with reddish-orange FIG. 73. Tangential section through 

 latex), the Campanulaceae, and in the 

 Compositae the Cichorieae (C ichor ium, 

 Taraxacum, Lacfuca, Scorzonera, Hieracium, 

 Tragopogon). 



There is little ground for the widespread idea that the laticiferous cells and 

 vessels also assist in the transport of materials. 



The MUCILAGE TUBES which occur in many Monocotyledons are in many 



respects similar to the 

 laticiferous vessels. Their 

 mucilaginous sap consists 

 of albumen, starch, glu- 

 cose, tannins, and inor- 

 ganic substances. 



the periphery of the stem of Scor- 

 zonera hispanica, showing reticu- 

 lately- united latex vessels, (x 

 240. After STRASBCRGER.) 



(3) LYSIGENOUS 

 I NTERCELLULAR 

 SPACES. Secretory 

 reservoirs frequently 



FIG. 74. Lysigenous oil-reservoirs from the leaf of Dictamnus arise as Spherical ir 

 fraxindla. A, Young. B, Mature after dissolution of the coll n , , ' -, 



walls. (ROTHERT altered from RASTER.) regular, Or tubular 



cavities by dissolution 

 of entire secretory cells, i.e. lysigenously (Fig. 74). 



These lysigenous secretory reservoirs arise from groups of cells in 



