i88 9 .] 



BOTANICAL GAZETTE. 



7 



suberin reaction. Several cases showed no inclination to the 

 ligneous reaction; summer, as well as plate cells, appearing 

 to be true cork, except along the edges where the break oc- 

 curred. All along these edges the walls of the exposed cells 

 and those lying next to them were colored a bluish purple, 

 the color diminishing gradually in intensity toward the cen- 

 tral portion of the wing. This is a noticeable and significant 



In almost every specimen tested the outer edges were 



This was not due to careless testing, as 



fact. 



not suberized. 



might be supposed, only enough of the chlor-iodide of zinc 



being used to affect the edges, for the sections were treated 



freely with this without a cover glass, and the reagent was 



dropped carefully on the center of the wing before it was 



allowed to reach the edges. The summing up of rive or six 



sets of experiments is as follows: the tendency is for the 



summer growth to form ligneous walls, plate cells always cork 



Q 



A few speci- 



mens showed no ligneous tissue, several only at the edges 

 along the lines of fracture, and still others gave a pure ligne- 



ous reaction throughout the entire summer cork. The same 

 mav be said of Acer campestre. 



In Acer monspessulanum the results were the same, ex- 

 cept here there were always ligneous cells along the line of 

 breakage. Euonymus alatus differed from the preceding 

 only in that the tendency to ligneous cells in the summer 

 growth was more marked. A few words in passing here 

 with reference to the morphology of these cells. In all ex- 

 amples studied, in e^se of the summer cells, the radial walls 

 were met by the tangential ones about in the center of the 

 cell, while in the plate cells the tangential walls were so cut 

 off from each phellogen cell as to meet each other, thus form- 

 ing a continuous line around the circumference. (See dia- 

 gram.) This construction of the summer cells is mentioned 



























— 









1 





1 



J__ 





i 



1 





1 



1 



1 



[ Sl'MME 



I Cells. 



be 



Plate 

 Cells. 



by Gerbef 2 in reference to the outer 

 cork layers of certain trees, which 

 layers are stretched by the growth 

 of the wood and phloem tissues 

 inside. In the case he cites, this 

 construction is accounted for on 

 the ground of its allowing this 

 stretching in the direction of the 

 circumference, the radial walls 



2 A Oerbcr, Die jahrliche Korkbildnng lm Oberfluchenperiderni einige Biiume. T r. 

 berichtderNaturf. Ges. zu Halle, Jan. 12. 1888. 



