1916] ROBERTS—EPIDERMAL CELLS OF ROOTS 497 
b) The chemical nature of walls 1, 2, 4, 6.—It will be seen from 
table III that a majority of the forms investigated have a wall 
made up of two parts, an inner membrane which gives the 
cellulose reaction with 75 per cent H,SO, and IKI, and an outer 
membrane which stains red with Ruthenium red, denoting 
pectin. That this membrane is calcium pectate is shown by the 
fact that on the addition of ammonium oxalate the membrane 
breaks down and calcium oxalate crystals are formed. It will be 
seen that some forms have a third membrane at the tip of the root 
hair. This membrane stains with all the callose stains, blue with 
aniline blue and resorsin blue, red with corallin soda. It will be 
noted that corn is the only form examined which has one membrane 
and that of cellulose. 
TABLE IIt 
CREMICAL NATURE OF ROOT HAIR MEMBRANES 
PLANT 
Inner Outer At tip 
Abtaias ca sess Thin cellulose | Thick pectin 
Amaranthus...... a . "6 
DAQey 42 3 < . 
Corie ous a ce" ee 
Corn salad... 3... Thin = Thick . Callose 
CABDARO 6 rae ad . ig 
Jaucus carota. : rn ti 
eepr GS hee | cate 
: : ‘ re ; 
Slageguaentee tn on gaeseees) wie ang res 
Sisymbrium...... Th: 4" Thin . 
"TFonacce: (25 62 ss : . Thick z 
Tradescantia Ae es sy : Thin Callose 
Ona n 
Ceraptopteris.....| Thick “ e « | Callose 
The walls 2, 4, 6, and z are alike in that they all have an inner 
membrane of cellulose and an outer membrane of calcium pectate, 
but differ in that the calcium pectate membrane on wall z is thicker, 
and in some instances in the presence of callose at the tip of the 
hair. The calcium pectate membrane on side 7 is continuous with 
the middle lamella of calcium pectate of walls 2, 4, 6. There is 
then a secretion of calcium pectate about the entire cell. 
