PROTOPLASM AND PLANT-GELLS. 



In reading the fore- 



these measurements as 15 mmm. and 35 m mtn . 

 going we may of course say 15 mi- 

 cromillimetres and 35 micromilli- 

 metres, but more commonly the 

 contraction micron is used, or even 

 the name of the Greelc letter : thus 

 we may say 15 microns, or 15 mu. 



(a) Make very thin longitudinal 

 sections of the tips of the larger roots 

 of Indian corn (Fig. 4) ; stain some 

 with iodine, which will turn the 

 protoplasm brown or yellowish 

 brown ; stain others with carmine ; 

 examine by the aid of the ^-inch ob- 

 jective. Make similar sections of the 

 tip of a young shoot of the asparagus. 



(6) Make successive cross-sections 

 of the root of Indian corn, begin- 

 ning with the tip and receding five 

 to ten millimetres. Note the 'vac- 

 uoles and use iodine and carmine. 

 Make similar sections of young as- 

 paragus-stem. 



(c) Make a longitudinal section of 

 the young part of a petunia-stem in 

 such a manner as to leave on each 

 margin a fringe of uninjured hairs. 

 Mount carefully in pure water. Ex- 

 amine at a high temperature (about 

 30° C. = 86° Fahr.) for a streaming 

 motion of the protoplasm in the 

 hairs. Place the specimen upon a 

 block of ice, and note that the move- 

 ment ceases. Warm again, etc. 



(d) With similar specimens observe 

 the effect of (1) iodine, which kills 

 and stains the protoplasm ; (2) alcohol, which kills and coagulates it ; 

 (3) glycerine, which withdraws water from it, and so collapses it. 



(e) Mount carefully in pure water a piece (2 to 4 centimetres) of 

 one of the young " silks " of Indian corn. The movement is well 

 seen In the long cells. Repeat the foregoing experiments. 



(/) The following may be taken also, viz. : the stamen-hairs of 

 Spiderwort, the epidermis of Live-for-ever leaf, fresh specimens of 

 the Stoneworts (Chara and Nitella), Eel-grass, etc. 



Fio. 4.— A little more than 

 half of a longitudinal section 

 of the tip of a young root of 

 Indian Corn. The part above s 

 is the body of the root, that be- 

 low it is the root-cap ; v, thick 

 outer wall of the epidermis ; m, 

 young pith-cells; /, young 

 wood-cells ; cr, a young vessel ; 

 s, i, inner younger part of root- 

 cap; a, a, outer older part of 

 root-cap. 



