1916] ROBERTS—EPIDERMAL CELLS OF ROOTS 495 
wall x. Sometimes the branch will be of less diameter than the 
main hair, as in fig. 8; and again branches will be of equal diameter, 
as shown in fig. 9. 
The stretched condition of the wall is evidenced by the fact that 
in some root hairs which are grown 
in moist air the membranes burst 
when the hairs are placed in water, 
or in a solution which has an 
osmotic pressure lower than that 
of the root hair cell, as shown in 
fig. 10; whereas plasmolysis occurs _ Fi6. 7.—Base of the root hair 
when the root hairs are placed in age eg vgs iadeeae ta era 
a solution of higher osmotic strength ee 
(fig. 11). The root hair remains normal when placed in a solution 
of an osmotic pressure equal to that of the cell content, as in fig. 12. 
Fre. 8 Fic. 9 
: Fics. 8, 9.—Fig. 8, branch of the root 
hair of less diameter than the main hair; was se 
fig. 9, branches of equal diameter. ee 
Fics. 10-12.—Fig. to, root 
: : hair grown in moist air and 
The following forms when grown in placed in water, membrane 
moist air and then mounted in distilled > ; 
water were found to burst immediately: . : : 
ialfa. barl bb 4 in a solution of an osmotic 
aan, PGUCY, CAbRSge, mustard, ‘Vd@S- pressure higher than that of the 
turtium, radish, Xanthium, and wheat. root hair; fig. 12, root hair 
These when mounted in a solution of Placed 
=e £ ; : osmotic pressure equal to that 
ucrose of an osmotic pressure equal tO  ¢¢ the cell content. 
the osmotic pressure of the cell in 
question remain unbroken, whereas plasmolysis occurs if a solution 
of higher osmotic pressure is used. The cells burst at the tip and 
a part of the content of the cell is ejected. The nucleus is thrown 
