492 



PROCEEDINGS OF THE ACADEMY OF 



[May, 



from the fifth outward is presented iu tabular form, as showing the 

 variation and increase in size of the several annual rings of wood 

 in the abnormally developed tissues of the stem. The variation in 

 the size, shape and color of the tracheids is a peculiarity of the 

 twelve-year-old stem studied. These variations are most marked 

 in the fourth and the eighth annual rings. The tracheids of the 

 fourth annual ring of wood are thicker thau the normal, and of a 

 decided yellow color. Those of the eighth annual ring are decid- 

 edly variable in shape. Some of the tracheids are circular in cross 

 section, others are elliptical, while others are rectangular and more 

 or less irregular. This departure from the normal structure of the 

 tracheids is directly traceable, the writer believes, to the stimulation 

 produced by the presence of the fungus in the tissues of the host 

 plant. 



Table VI. 



A comparison, however, of the width of the several annual rings 

 of older and jounger stems shoAvs that the increase in the number 

 of tracheids is marked, especially in the immediate neighborhood of 

 the hvphte. There is, however, not that marked increase which is 

 noted for the stems abnormally swollen by the action of the myce- 

 liiun of Gymnospormigium bi-septatum. The same brown patches 

 of pathological tissue are seen in branches an inch and a quarter in 

 diameter. Here, if the disease is confined more especially to the 

 smaller branches, the brown areas are more rounded and appear as 

 isolated brown specks when a cross-section is made. The smaller 



