Roots of Some Rosaceous Genera. 59 
Group Pomee.—The following four species were selected for 
study: Lviobotrya japonica, Pyrus communis, P. japonica, P. 
Malus. All of these genera show compactly arranged cork 
cells with no intercellular spaces. There is no separation into 
annular zones with the exception of the cork region of Pyrus 
japonica. In Eriobotrya japonica the cells have the usual 
tabular form found in this group, but the radial walls are 
much thickened, giving to them the characteristic appearance 
of endodermal cells; the cell walls also are deeply pigmented 
in specimens studied during early September. In Pyrus 
Malus the cell walls of specimens studied in early September 
are not pigmented, but within the cell cavities beautiful golden 
pigment is found. 
The marked arrangement of the cork region into annular 
rings, each of which may again be made up of dissimilar rows, 
has led to the belief that these may each represent a year’s 
growth. Since the vascular bundles do not so clearly indicate 
in roots as in stems the age of the root, this point has not been 
definitely settled. It is of interest to note that in the roots of 
Geum atrosanguineum, Spirea Filipendulaand Agrimonia par- 
vifiora studied in December, the uniseriate flattened layer is 
the one which is always found next to the phellogen, indicating 
that this layer is the last formed during the year. 
Hartig and Sanio for the birch stem, and De Candolle for 
Quercus Suber have pointed out the fact that the number of 
zones of cork correspond with the number of years to which 
the stem has attained. 
(6) Suberization of the Periderm.—With a view of ascertain- 
ing the amount of suberization of the different annular layers 
of the periderm or cork, many chemical tests have been used, 
among which may be mentioned iodine and sulphuric acid— 
in the proportions suggested by Russow—alcannin, chlorophyl 
extract, potassium hydrate, Schultze’s solution, osmic acid, 
double staining with ammonia fuchsin and aniline blue, also 
chromic acid. In the groups Porentillee, Agrimoniee, Spi- 
