36 



A TEXTBOOK OF BOTANY [Ch. Ill, 5 



this state has an appearance and texture which most ob- 

 servers agree in likening to a jelly, a rather thin and clouded 



jelly, which holds various 

 small solid bodies, mostly 

 food grains, in suspension. 

 Scientifically, its constitution 

 is described as colloidal. . In 

 the oldest cells it often be- 

 comes even more thin and 

 watery than here, though 

 hardly ever a true fluid; 

 and the clouded appearance 

 often vanishes, leaving the 

 protoplasm nearly transpar- 

 ent, in which case it is almost 

 completely invisible unless 

 killed and dyed by special 

 stains. In much younger 

 cells, it is more viscous, be- 

 coming a gelatinous solid; 

 and in resting seeds and 

 buds, which have given up 

 most of their water, it be- 

 comes even as firm in tex- 

 ture as dry gelatine or horn. 

 Since some of the food parti- 

 cles have a yellowish tint, a 

 large mass of such proto- 

 plasm has a distinctly yellow 

 color, as seen in the young 

 growing tips of roots, or the 

 central parts of young ovules. 

 There is usually an obvious 

 relation between the condi- 

 tion of the protoplasm in 

 these respects and the function of the cell. 



Fig. 12. — The appearance of the 

 protoplasm in a typical hair-cell of 

 a Gourd, as seen projected against 

 a black background ; greatly mag- 

 nified. (Reduced from Sachs, 

 Lectures on the Physiology of Plants.) 



