FORMATION OF CELLS— TISSUES 



323 



The three forms of tissue so far described, viz. parenohj'ma, 

 prosenchyma, and vascular tissue, combined in various ways, 

 constitute the greater part of the plant body. Besides these, 

 other forms are foimd in certain cases, having, however, a much 

 more limited distribution. We may here briefly describe the 

 most important of these. 



Lnticifei-nun Tissue. — Of this, two types occur. In the 

 Enphorbias, and some plants belonging to the Ajinci/narrrr and 

 Asr1rpiaihirr{r, long, much-branched cells occur irregubarly dis- 

 tributed throughout the plant {;fi/j. 698). They have often thick 

 walls, and are filled with a curious milkv-looking fluid known as 



Fig. 697. 



Fig. 698. 



Fii/. 097, LatioMeroiis ye.ssels (cell fusions) in Seorzonera root, x 260. 

 Fiij.MH. Part ol laticiferous cell from stem of Euplwrlia splendens. x 260. 



latex, -which, has given them the name of Jaticiferous cells. In 

 the Compositcr, Papavcracco!, and other Natural Orders, ramify- 

 ing tubular structures are found, much like the former, but com- 

 posed of rows of thin-walled parenchymatous cells, the partiLion- 

 walls of which have been absorbed. These, from their contaimn;? 

 a similar milky-looking or watery latex, are known as laticiferoiis 

 vessels {fig. 697). Laticiferous vessels generally form an anasto- 

 mosing network. 



A modification of this tissue is found in some monocotyle- 

 donous plants, forming what are known as utricular vessels. 



