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 

 figure. The addition of Ruthe- 

 nium red now gives no color 

 Figs. 16, 17.— Two layers of the except a faint tinge of pink 

 root hair membrane; fig. i 7l Nasturtium about tfae crystaIs due to the 

 root hair after being in ammonium . , 



oxa l ate 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 HC1 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 



