486 PROCEEDINGS OF THE ACADEMY OF [May, 



liyphse of cndotropic mycorliiza. Groom'"'' and ^Magnus-' have lioth 

 worked upon this problem, and Ijotli botanists have shown that in 

 tlie case of the hyphse of mycorhiza fungi they enter a cell because 

 they are attracted thither by a chemotropically active substance 

 and grow toward the nucleus, because that substance is present 

 there in optinuim proportions. These investigators conclude that 

 the chemotropically active substance attracts the hyphje and is 

 manufactured in the cell infected, and particularly in the vicinity 

 of the nucleus of that cell. No clearly defined relationship of this 

 kind is discoverable in the medullary ray cells of the white cedar. 

 The hyphse run straight through many of the cells without devi- 

 ating from their course. 



This distribution of the mvcelium in G. biseptatum seems to be 

 similar to the distribution of liyphse in G. Ellisii. as described by 

 Farlow. The mycelium of this species, according lo I'arlow, is of 

 rather large size and in cross-sections of the stem is seen to follow 

 the medullary rays, sometimes extending nearly to the center of 

 the stem, and occasionally forming partial circles between the 

 annual rings. The greater part of the mycelium in G. Ellisii, 

 according to Farlow, is found near the cambium, it collects 

 in masses in the bark to form the sporiferous bodies which originate 

 at some little distance beneath the surface. 



JNIycelium of Gymnosporaxgium Ellisii. 



The mycelium of GymnosporaiKjium Ellisii is more copious than 

 that of G. biseptatum, and its activity seems to be more marked 

 in producing pathological changes in the tissues of the host. It 

 may be traced in both radial and tangential longitudinal sections to 

 the best advantage. The development of the hyphse of the my- 

 celium in the sections studied by the writer is in a longitudinal 

 rather than in a transverse direction (fig. 24). The main hyphse 

 of the mycelium are longitudinal ones, and these anastomose with 

 each other by the formation of short hyphse developed at right 

 angles to the longitudinal ones. The course of the main hyphse is 

 approximately a straight one, although of necessity there is some 



^^ Groom, On Thismia Asero? (Beccari) aud its ^lycorhiza, Annals of 

 Botany, IX, pp. 327-3()0. 



^"Magnus, Wehnkr, Studieu an der endotroplien Mycorhiza von 

 Neottia nidus-avis L., Jala-buchcr fur wissenschaflliche Bot., 19u0. p. 

 205. 



