498 BOTANICAL GAZETTE [DECEMBER 
The relative thickness of the membranes having cellulose 
and pectin layers varies with the different plants, the cellulose 
layer being uniform over the hair, while the pectin is quite often 
thinner near the tip. Fig. 16 shows the tip of the root hair of 
Nasturtium with the two layers, the outer of pectin, and the inner 
of cellulose. Fig. 17 shows another Nasturtium root hair after it 
had been in ammonium oxalate; the calcium pectate has been 
changed to calcium oxalate and 
pectic acid. The calcium oxa- 
late crystals are shown in the 
aad aE figure. The addition of Ruthe- 
Fic. 16 Fic. 17 nium red now gives no color 
Fics. 16, 17.—Two layers of the except a faint tinge of pink 
root hair membrane; fig. 17, Nasturtium about the crystals, due to the 
root hair after being in ammonium Z 4 ee 
owalate: presence of pectic acid. Within 
the cell there are always masses 
of pectic substances; this is not calcium pectate, as it does 
not break down on the addition of ammonium oxalate, but still 
gives the color with Ruthenium red after treatment with ammo- 
nium oxalate. 
Either of the membranes may be removed by treating the cell 
with their respective solvents. The calcium pectate membrane 
is soluble in 2 per cent HCl and 2 per cent KOH, the cellulose is 
soluble in copper-oxide-ammonia. 
The fact that the soil particles are held to the hair by the trans- 
formation of the outer layer into mucilage has long been accepted, 
but what that mucilage is has not been known. In the case of corn 
growing in the soil or in quartz sand, the mucilage was found to be 
of cellulose, whereas in a Coleus root growing in the soil the soil 
particles are held to the hair by a pectin mucilage. 
It has been known that the epidermal portion of the seedling 
from which hairs arise stains brown when put in a 2 per cent 
solution of potassium permanganate, and that the region just above 
that of the hairs is not colored by the solution. This has often 
been used to differentiate in a general way the stem and root regions 
of a seedling. The chemical nature of these walls was determined. 
The external wall of the epidermal cells above those forming root 
a 
