PARENCHYMATOUS TISSUE 



253 



pj 



the growing point. In the mesophyll (or middle soft 

 part) of leaves the elaboration of plant-food takes place. 

 Intercellular spaces filled with air and other gases are com- 

 mon in this tissue of leaves, as well as in parenchyma of 

 other parts of the plant. 



410. To stud} growing points, 

 ii-i' the hypoootyl of Indian corn 

 which lias grown aboul one-half 

 inch. The materia] should be placed 

 in 4<) per cent alcohol for a few 

 hours, then in 7< per cenl for the 

 same length of time, and then in !."> 

 per cenl nut il ready for use. Blake 

 a series of Longitudinal sections, 

 stain with hematoxylin, mount, and 

 then select the middle <>r median 

 one for si ndy wit h t he high power. 

 Note these points (Fig. 395): (") 

 Root-cap beyond the growing point. 

 ( b ) The shape of t he end of the 

 rool proper and i he shape of i he 

 cells found there, (c) The group 

 of cells in the middle of the first layers beneath the 

 root-cap. This group is the growing point, (d) Studj 

 the Blighl differences in the tissues a shorl distance 

 back of the growing point. There are four regions: the 

 plerome, BeveraJ rows of cells in the center; the endo- 

 dermis, composed of a single layer on each side ; the 

 periblem, of Beveral layers outside the endodermis, ami 

 t In- dermatogen, <in the outer edges. Make a drawing of 

 the section. If a series of the cross -sections of the hypo 

 cotyl should be made and studied, beginning Dear the 

 growing poinl and running back some distance, it would 

 be found thai these four tissues become more distinctly 

 marked. The central cylinder of plerome will contain the 



trowing [Hiint 



[mlinn 'm. il, </ 



dodermii 

 i:il group i 

 t propei 



