62 Bunting — The Structure of the Cork Tissues in 



Pyrns Mains, Pyrus communis and Eriobotrya nuclei were not 

 demonstrated. In these species the cork cells were very 

 small and surrounded by heavy cell walls, hence it was 

 difficult to prepare sections, and thus reach definite conclusions 

 as to the presence of nuclei. 



(^/) Starch in the Cork Region. — In making tests for cork, by 

 the use of iodine and sulphuric acid, it was observed that 

 starch was present in the cork region, hence iodine was used 

 with the different Rosaceous species in order to determine in 

 what species starch was present in the roots. As a result of 

 this test, starch was found in all the Rosaceous roots. Among 

 the herbaceous and shrubby species it is observed in large 

 quantities ; though a relatively larger amount is found in the 

 younger layers of cells toward the cork cambium, than in the 

 uniseriate flattened cells with pigment contents, or in the cells 

 which are peeling off, although it may be found in all of 

 these. In Prunus vii'giniana, Pyrus Alahis, P. co?nmunis and 

 Eriobotrya japonica starch is also found in the cork cells, 

 although in the roots of these species the quantity is not so 

 great as in herbaceous roots. As would be expected, the 

 amount of starch varies with the time of year in which the 

 roots are studied. In late autumn, winter and early spring the 

 periderm cells are loaded with starch, while the amount is 

 appreciably decreased in the late spring and summer. This 

 fact seems to indicate that the starch is used by the root, and 

 that the cork cells as well as the other cells are reservoirs in 

 which it can be stored. It would be verj' desirable to make 

 tests for sugar, when the growth of the root has commenced, 

 in order to determine definitely whether the starch found in 

 this region is a reserve or a waste product. 



(r) Pigment of the Cork Region. — Many of the genera of 

 Rosacea; contain pigment in some or all of the cells, as well 

 as in the cell walls, it is however most frequently found in the 

 uniseriate flattened layer, where such an annular layer is 

 present. In sections of Pyrus Jl/a/us all the cells contained a 



