314 BOTANICAL GAZETTE [NOVEMBER 
would explain the presence of acid in the soil. Again, ODEN (3) 
found in the plants that he examined a gelatinous material of the 
nature of pectic acid, and Manern (1) found that pectose is often 
formed in young cells before cellulose, and that the middle lamella 
is calcium pectate. He (2) also found that pectose can be changed © 
to pectic acid or pectin by gently heating in 2 per cent hydrochloric 
acid. 
SAMPSON (5), in investigating abscission of the leaf of Coleus, 
found that there was calcium pectate in the middle lamella just 
before the time of abscission, but that the calcium was lacking at 
abscission, and discovered that this was due to the pectic acid 
forming so much more rapidly than the calcium was supplied that 
the middle lamella was broken down. Miss Roperts (4) also 
examined root hairs of a number of seedlings grown in moist air 
and found that they all had a layer of pectic material outside the 
cellulose wall, and often at the tip of the hair there was a layer of 
callose. 
In order to determine whether this condition is general, the 
root hairs of twenty economic plants grown in sand and in loam were 
examined, and those of a few seedlings grown in Knop’s solution. 
These seedlings were selected with the idea, first, of getting as great 
range as possible, and secondly, of comparing several in the same 
or closely related genera. These root hairs were tested micro- 
chemically for cellulose with iodine and 70 per cent sulphuric acid, 
which turns cellulose bright blue; for callose with resorcin blue, 
which causes callose to swell and to turn blue; for acidity with 
neutral red (and later with the Clark and Lubs indicators to 
determine the degree of acidity); for calcium pectate with ammo- 
nium oxalate, which unites with the calcium pectate when calcium 
oxalate crystals and ammonium pectate are formed; and for pectic 
material in general with ruthenian red. Of the special forms 
of pectic material chiefly found in plants, pectose is found 
especially in young tissues, is insoluble in water, but can be 
changed to pectic acid or pectin by gently heating for twenty 
minutes in a 2 per cent solution of hydrochloric acid. Pectin is 
soluble in water, and pectic acid is soluble in a 2 per cent solution 
of potassium hydroxide when gently heated for twenty minutes. 
