/ 



22 THE PLANT CEL 



of the pulp of a tomato or of climbing bitter-sweet berries, 

 using the juice of the fruit as a mounting medium, jjraw and 

 measure chromoplasts of different forms and colors. Tiiit the 

 drawings as near the natural colors as possible. 



6. To see in a comprehensive way that cell-walls nuty be 

 of different kinds mount thin cross sections of old siem o. ..ris- 

 tolochia (Fig. 24), or of some other wocdy stem, in u...erent 

 reagents for differentiating cell-walls. Examine a sec.Oii urst 

 in water to note the natural colors of the walls. Filler a^ a/ the 

 water and add a drop of chloroiodide of zinc. . net . hile 

 the cell-walls of some of the tissues will be colored yei.u and 

 others purple. The purple walls are cellulose aid li.c- cilow 

 are lignified, suberized or cutinized. 



Mount another section in aniline sulphate and on! lig- 

 nified walls will be colored yellow while the others w ,eft 

 unstained. Mount a thiid section in phlorogluv:i) u ue 

 lignified walls will be colored pink while all others ^• in- 

 changed. Finally sections left for se\'eral hours in . are 

 of alcannin will have the cutinized and suberized ■ >ne 

 stained pink. See under these reagents in Chapter W 



7. Mount a bit of Nitella in a drop of water ard ^ .; d ow 

 of the cytoplasm. With a micrometer eyepiece ard a nn n e 

 to tick off seconds determine the rate of flow per se d. 



Remove a filament from a young bud of Trade r- 



ginica and mount it in a drop of water. Study ti.e _ lu. on 

 of the cytoplasm in one of the cells of a hair grow g froni , e 

 filament. How does it differ from Nitella as to .be mam er 

 and rate of flow? Draw a cell, using Fig. 9 a? pattern lor 

 line-work and stippling. 



8. Mount in water some of the mealy green scum sometimes 

 found at the surface- of stas;nant ponds. If it is found composed 

 of motile green bodies with a red eyespot, these individuals are 

 Euglena viridis. Note the beating back and forth of the color- 

 less flagellum at the eyespot end, and now by drawings the 

 different forms which a single Euglc"^ 's found to -T^e 

 within a short time. 



