1902.] XATURAL SCIENCES OF PHILADELPHIA. 487 



bending from a straight Hue as they run from ti-acheifl to tracheid 

 (fig. 25). Some annual rings are noted for the considerable num- 

 ber of hyphre preseut. Others are marked by the small number 

 and weak development of the hyphse. The color of the hyphre 

 is an umber-brown, practically the same as that of the hyph?e of 

 Gymiiosporangmm biseptatum. Occasionally hyphre in G. Ellisiia.ve 

 found that are yellowish-brown in color. The hyphal strands are 

 characterized by the well-marked transverse partitions, which are 

 evident even under the low power of the microscope. It may be 

 remarked here that the general coui"se of the mycelium can be 

 clearly followed by the low power alone. The mycelium is more 

 abundant in the cortex and comparatively less abundant in the 

 xylem. Some peculiarities of structure of the hyphie of this 

 species easily differentiate it from G. biseptatum. The hyphre of 

 G. Ellisii form, as revealed by the high power of the microscope, 

 a somewhat irregular reticulum (fig. 24). These hyphse are char- 

 acterized by the presence of larger or smaller nodose or ventricose 

 hyphal cells (figs. 25, 26, 27), which are found in considerable 

 numbers in the length of each hyphal strand. These swollen or 

 enlarged cells are found most frequently iu the irregular intercellular 

 spaces, filled with brownish material produced by the pathological 

 changes induced iu the host by the growth of the fungus. Occa- 

 sionally these ventricose hyphal cells are found as lateral branches 

 of the main longitudinally directed hyphse. Their shape may be 

 sphei'ical, ellipsoidal, oblate-spheroidal, napiform or fusiform (figs. 

 25, 26, 27). They' are of the same umbei'-browu color as the 

 other unenlarged hyphal cells, and are most numerous in the cor- 

 tical region and in the aforementioned pathological areas filled witix 

 l)rowu material. 



Relation of Hyph^ of G. Ellisii to Host Cells. 



The course of the hyphje in the stem may be briefly described as 

 follows: The straight hypha runs through the lunaen of the 

 tracheid until it comes to a bordered pit which lies iu the direction 

 of its growth (figs. 24, 24a). This bordered pit is entered, and by 

 a solution of the middle lamella of the cell wall at this point it 

 crosses to a neighboring tracheid, when it again takes a longitu- 

 dinal direction. Sometimes two or three tracheids are crossed by 

 the hypha before it again takes an u[)-and-dowu coui-se (fig. 24). 



