TISSUE SYSTEMS 25 i 



41G. SCLERENCHYMATOUS OR SCLEROTIC TISSUE. - 



Sclerenchyma cells are hard, Dot elongated, often some- 

 what spherical, and their thickened walls are provided 

 with simple <>r branching canals. The cells of this tissue 

 ar.- illustrated by the common grit cells of the pear and 

 some other fruits. They are also found in the coats of 

 many seeds, in nut shells, in the pith of some plant-. 

 Hold a large gritty part of a pear between two pieces of 

 smooth elder pith or cork and make free-hand sections. 

 .Mount in water. Make a drawing of a single cell showing 

 thiekmss of wall. size of central cavity, wall markings. 

 Note the general shape of the cells. 



417. LATICIFEROUS TISSUE. That tissue found ill many 

 plants which contain a milky liquid is called laticiferous 

 tissue. There is no fixed type for the vessels which carrj 

 this fluid, as they vary greatly in differenl plant-, being 

 simple in the asclepias (milk weed . and complex in the 

 dandelion. 



41S. TISSUE SYSTEMS. The part- of complex plants 



max be conveniently grouped into three tisstu systems: 

 (1) Fibro-vascular tissue system. This is composed of 

 fibro-vascular bundles. The fibrous framework of root-. 

 stems, and leaves is made of fibro-vascular bundles. 

 (Fibro-vascular means fibrous or long and -lender, and 

 having long openings or channels.) Bach bundle is 

 composed of two fundamental parts: phloem and xylem. 

 The basl fibers maj or maj not be present. Phloem is 

 another name for the soft bust or sievt tissue, while xylem 

 [g the name of the lignified or wood} pari and is com- 

 posed chiefly of the wood cells, tracheitis, and ducts. In 

 stems of dicotyledons (exogens), these two part- "t the 

 bundle are separated bj cambium, a meristematic layer giv- 

 ing rise to xylem on one Bide and to phloem <>n the other. 

 For types of bundles, see oexl chapter. (2) Fundamen- 

 tal tissue system. This is composed of the parenchyma- 



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