Roots of Some Rosaceous Genera. 6 1 



condition in various cork cells which show special reactions to 

 certain reagents. This fact has been suggested as a possibility 

 by De Bary, but since in the case in point the species of 

 PnniecE and Poinece were uniform in their results with those 

 from the oak stem, I am inclined to consider that they are not 

 so useful as tests for cork when the amount of cork present is 

 quite small. 



(<-) Presence of Nuclei in Cells of the Cork Region. — The 

 stains which were employed for the purpose of demonstrating 

 the nuclei were Bismarck brown, hsematoxylin and picroni- 

 grosin. By the aid of these stains nuclei were found in 

 Potentilla noi-vegica, both in the flattened uniseriate layer of 

 cells and in the multiseriate layers, even so far as where the 

 layers were sloughing off. In Geum album and G. atrosangui- 

 neum nuclei are observed in the outermost layer of large cells ; 

 when the periderm consists of five layers of cells, nuclei are 

 also found in the layers of small cells in the first species. In 

 Fragaria indica nuclei are present in the second multiseriate 

 layer of cells. In Waldsteinia geoidcs nuclei have been noted 

 in the eighth layer of cells of the periderm, the nuclei being 

 found both in the cells with and without pigmented contents. 

 In Agrimonia Eupatoria nuclei are found both in the uniseriate 

 layer containing brown pigment, and in the multiseriate zones, 

 and can be recognized even so far out as the eleventh row of 

 cells. Nuclei are shown in the phototype of Agrimonia, but 

 this root is a comparatively young one. In Agrimonia parvi- 

 flora nuclei are demonstrated in the third uniseriate layer, as 

 well as in the third multiseriate one. In Alchemilla pyrenaica 

 nuclei are found in the eighth row of the periderm, and in 

 Spircea Filipendula in the tenth periderm layer. In Rubus 

 occidentalis nuclei are noted both in the uniseriate and multi- 

 seriate layers, being present even in the eighth row of the 

 periderm. In Rosa nuclei are detected in the eighth row of 

 the periderm ; these may persist both in the cells containing 

 pigment and in those devoid of pigment. In Prunus vi)gi?tiana, 



