«J4 Bunting-^Tlie Structure of the Cork Tissues in 



lines to the AgrimomccB ; from this group or from ancestors 

 intermediate between it and Potcntillea there may have 

 diverged on the one side the ancestors of Rosecz, and on the 

 other those of the Spirceeee. A more direct line would lead 

 to the Rube(2, the three just named in their highest examples 

 having all reached about the same degree of differentiation. 

 Lines of specializing development would lead respectively 

 from the Rubece to the Pruiiece, AmygdalecB and Pomeez. In 

 my investigations upon the cork region of the above Rosaceous 

 genera, the degree of specialized development reached in the 

 cork cells of the different groups would seem to indicate in 

 this respect such a relationship of the groups within the order. 

 {h) Summary of Results.— \. Large intercellular spaces are 

 present in the cork region of the herbaceous genera, smaller 

 spaces in the shrubby genera of the order Rosacecz. They are 

 absent in the arborescent genera studied. 



2. A marked characteristic of the herbaceous and shrubby 

 genera of Rosaccce is the annular arrangement of the cells of 

 the periderm region. In the arborescent specimens studied, 

 the annular arrangement is not a feature of the periderm 

 region. Results obtained from the study of this annular 

 arrangement, suggest that each ring corresponds to a year's 



growth. 



3. In herbaceous and shrubby species, a notable feature is 

 the presence of a uniseriate layer of cells in which a lamella of 

 suberin is present in the cell walls, this may or may not be 

 present in the multiseriate layers. In very young roots the 

 condition noted in Vines' textbook is sometimes found, namely 

 that the radial walls alone of the uniseriate layers contain 

 lamellae of suberin. 



4. Nuclei have been noted, alike in the uniseriate layers in 

 which the cell walls and contents are pigmented and in the 

 multiseriate layers. These nuclei have been observed in some 

 regions in the cells of the eighth layer. 



5. Starch is present in cork cells of all the Rosaceous genera 



