76 COMPENDIUM OF GENERAL BOTANY. 



(b) The Laticiferous Tissue. 



An important conclusion to the subject under consideration, 

 that is, the cell- forms which conduct water and food substances, is 

 the discussion of the milk- tissue or laticiferous tissue of plants. 

 The laticiferous tubes occur most frequently, but not exclusively, 

 in the albumen -conducting tissues of the vascular bundles ; they are 

 also found in the outer parenchyma and in some other tissues. 

 This tissue-system affords an excellent illustration of the correctness 

 of this statement : Different modes of development produce physio- 

 logically similar structures. There are : 1, simple, 2, complex, milk- 

 tubes. In the mature state both present the appearance of a much- 

 branched system of canals, though even in the earlier stages close 

 examination will reveal the distinguishing characteristics of the two 



a 



FIG. 44. Laticiferous vessels (diagramatic). 

 a, Branching ; 6, anastomosing. 



forms of tissues. The complex milk-tubes (Cichoriacece, Papave- 

 racece) form a reticular structure by the joining of many branches 

 ("anastomosing"); the simple (Euphorbiacece, Apocynacece^ Mo- 

 racece) tubes seldom anastomose, or perhaps not at all. To deter- 

 mine whether a given milk-tissue is simple or complex is one of the 

 difficult problems of plant- anatomy, and conclusions differ with 

 different authors. 



The names indicate the mode of development of the two forms 

 of tissue. The complex milk-tubes are cell-fusions in which the 

 remnants of the unabsorbed cell -walls are visible at the points of 

 union (see Fig. 44, I). The simple forms can be traced to a few 

 milk-cells which exist in the embryo of the plant, and which sub- 

 sequently grow in length and branch in a manner similar to the 

 hyphse of fungi (Fig. 44, a). As already stated, anastomosing (fu- 



