466 PROCEEDINGS OF THE ACADEMY OF Play, 



from ihe basal end of the twig, where the swelling is largest, toward 

 the distal end, where the growth merge? with the normal diameter 

 of the branch (fig. 8 ). The abnormalities on the lateral branches 

 of two other young trees of white cedar are marked, because the 

 secondary branches have increased considerably in number and 

 have assumed a fastigiate habit, radiating upward and outward 

 from an approximately common point. As many as twenty small 

 branches, all about six inches long, are to be counted in a single 

 fasligiation (fig. 8). The surface of the Imrk in these specimens 

 is raised into vesicular roughenings, which condition seems to 

 precede the formation of the rectangular plates of bark by some 

 interval of time. 



Normal 8tkm Structure of White Cedar. 



According to Prof. Sargent," " the wood of Cupressiis thyoides 

 is light, soft, not strong, close-grained, easily worked, slightly 

 fragrant, and very durable in contact with the soil. It seasons 

 rapidly and perfectly without warping or checking ; it is light- 

 brown tinged with red, with thin lighter-colored sap-wood, but 

 grows darker with exposure, and contains dark-colored, conspicu- 

 ous nari'ow bands of small summer-cells, and numerous obscure 

 medullary rays. The specific gravity of the absolutely dry wood 

 is 0.3322, a cubic foot weighing 20.70 pounds." 



The sections, made with a hand-plane, were stained with three 

 different stains, viz., methyl-green, Bismarck -brown and a mixture 

 of methyl -green and acid-fuchsin used as a double stain. The 

 histological details of the stem in an uudiseased state are as follows : 

 The pith of a twenty-one-year-old stem with wood three-eighths 

 inch diameter is almost entirely absent. Its place is filled by the ' 

 clo.sely aggregated spiral tracheee which compose the region known 

 as the protoxylem. From this small contracted protoxylem radi- 

 ate toward the cortex the primary medullary rays and the wedges 

 of xylem. The medullary rays are numerous, but obscure. They 

 consist in the cross-section of but a single row of thin-walled 

 parenchyma cells which are six times longer than broad. The 

 wedges of wood are narrow, their radial limits being defined by the 

 medullary rays. The following table shows the variation in the size 

 of the annual rings, as determined by a count under the microscope 

 '' Sargent, Sihd of North America, X, p. 11-*. 



