490 



of larger dead cell groups which were enclosed by a living parenchyma wall, 

 circular in form; thereby they formed a figure resembling an eye (Fig. loi). 

 In the centre of this eye-like figure frequently a depression was formed (h), 

 which was lined by slightly browned, at times almost colorless, cells («)• 

 In comparing the pictures, which vary in each section, one became convinced 

 that these cells, enclosing the cavity, corresponded to a resin canal lining 

 and at times had been pushed out like vesicles into this cavity. This was 

 bounded on the outside by a dead bark parenchyma (/>), with only rarely 

 collapsed cells and usually of natural size, of which the contents and walls 



i7? 



J^— 



~ Isolated dead bark 

 n slightlv colored or 

 exhibits clearly the > 

 region of the resin c; 



iwn homogeneous contiiits, // cavity in the dea<l heart of the tissue. 

 -ss lining of the central cavils which, in structure and conii>osition, 

 le liuinR of a resin canal, /i brow ii liark parenchyma cells from the 

 ■ly impregnated with resin, ,.' parenchyma elongated like plates an<,l 

 ing starch, > fi normal bark p.arenchyma. 



were impregnated with resin. By clearing the sections, dififerent groups 

 of oxalates could be recognized in the dead parenchyma as well as cells with 

 grains, which should be considered as starch impregnated v^'ith resin. This 

 dead tissue was bounded on the outside by the above mentioned circular zone 

 of plate-like cells, which in their arrangement resembled a cork overgrowth 

 when treated with chloriodid of zinc, but gave a cellulose reaction in their 

 walls and were often filled abundantly with starch and small drops of resin 

 (r). This overgrowth of the dead tissue centre, which gave the eye-like 

 appearance to the frost wound, often passed over into the normal bark par- 

 enchyma (rp) which here and there left recognizable traces of starch. 



