274 TAYLOR— ON THE PRODUCTION OF 



Castanea — "Paragon" 



Material and Methods 



The material used in the study of tissue modifications in the Chestnut 

 consisted of small grafted "Paragon" trees obtained from a large orchard 

 near Martic Forge, Lancaster County, Penna. In the hope of thereby 

 controlling the Chestnut Blight, Dr. Rumbold had injected into different 

 trees here during 1915 and previously, a large variety of chemicals (2). 

 On the 7th and 8th of November 1916, the writer went with Dr. Rumbold 

 to Martic Forge and cut down a number of trees. Sections of the trunks 

 of these were sent in to the laboratory and preserved for study. 



The collection comprised trees that had been injected with various 

 chemicals, others that had been badly infected with the blight, some in 

 which large cankers had been carefully cleaned away a year or more previ- 

 ously, and others with minor injuries or normal structure for comparison. 

 As a result of the various vicissitudes that they had undergone, many 

 showed an extremely gnarled and twisted exterior with but little Hving 

 wood, while a few were completely dead. 



In all cases a hand-lens examination of the material preceded prepara- 

 tion for sectioning on the microtome. Each specimen was sawn thru 

 at the point to be examined, and the surface smoothed with a sharp 

 chisel, when examination of the surface with a good hand-lens 

 (X 10) sufficed to show clearly the distribution and general nature 

 of any abnormal structures in the peripheral wood or the bark. Material 

 so prepared and coated with glycerin photographed easily (Plate LXXIV, 

 Fig. 11). Representative specimens of the material were cut out, 

 treated with hydrofluoric acid to remove the siKca, washed, and embedded 

 for sectioning in celloidin in the usual way. 



Normal Histology of Castanea — "Paragon" 

 Before describing in detail the various alterations in the tissues 

 found in the neighborhood of the wounds of Castanea, it is necessary 

 that the normal structure of the stem be discussed. 



The Pith in stems of the age used had long been lignified and dead. 

 Lignification seems to occur during the first year. 



The Wood consists of elongated fiber cells and of prominent pitted 

 vessels. These latter are mostly formed in the spring, producing a 

 distinctly ring-porous wood. The walls of these pitted vessels are not 

 very greatly hardened, and the pits are small and transverse (Plate 



