Roots of Some Rosaceous Genera. 59 



Group Pomece. — The following four species were selected for 

 study : Eriobotrya japonica, Pyms comimmis, P. Japonica, P. 

 Mains. 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 oi 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 

 Ge7ini atrosangtdneum, SpircBa Filipendiilaz.x\A Agrbnonia par- 

 viflora 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. 



{b) 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 PotentillecZy Agrimoniece, Spi- 



