38 



that some of the epidermis cells are slightly higher than the 

 others; some bulge out considerably above the level of the leaf 



surface (Fig. 8). Soon this protrusion is separated from the 



mother cell by a cross-partition (Fig, 9), and is afterwards raised 

 still higher by the intercalation of two (rarely one or three) pedi- 

 cel cells (Fig. 10). At the earliest stages all the cells are filled 

 with turbid, granular protoplasm, which, as the hair increases in 

 size, is replaced, or rather, crowded to the wall of the cell by a 

 yellowish white mass of mucilage, which makes its appearance in 

 the interior of the cell (Fig. 10). 



This coherent, bulky, homogeneous, slightly translucent sub- 

 stance keeps increasing with the growth of the hair, closely sur- 

 rounded by the layer of protoplasm, in which currents become 

 plainly visible. As the hair gradually elongates, either horizon- 

 tally or vertically, globular vacuoles are formed at various places 

 in the cell. They finally merge into one or two, sometimes 

 three or four, each occupying the entire width of the hair, and 

 confining the mass or masses of mucilage between them (Figs. 

 II, 12, 14). Besides the parietal layer, thin strands and plates 

 of very actively streaming plasma may be noticed, which extend 

 all over the cell, carrying with them smaller and larger globular 

 microsomata (Figs. 11, 12). Streaming protoplasm is also seen 

 in the narrow space between the cell wall and the mucilage. In 

 hairs in which the plasma is at rest, the microsomes at first create 

 the impression of being imbedded in the mucilage ; but even 

 then exact focussing will destroy this illusion. The nucleus is 

 found only with difficulty. 



In some of the hairs, at various points of the surface, a slight 

 swelling or bulging of the outermost layer of the epidermis may be 

 noticed ; in others the swelling has extended over a considerable 

 portion of the hair (Fig. 11), and with a great many others, a 

 complete, closed, bubble-like sac, as described above, surrounds 

 the entire hair (Figs. 12, 14, 16). The sac, when examined 

 without the application of any reagents, appears filled with an 

 almost transparent, homogeneous, mucilaginous substance. It 

 keeps increasing in size until it reaches, in many instances, sev- 

 eral times the length and width of the hair, and at Ust it bursts 



usually at the top. 



I 



