STUDIES IN SYMBIOSIS. 1., 



smaller than the other exodermal cells; the larger esodermal cells have little 

 protoplasm; the passage cells have considerable protoplasm and a large nucleus. 

 The fungal hyphae passing from the sheath to the inner tissues of the root 

 traverse the passage-cells (Text-figs. 11, 12, 24). The thin cellulose wall of 

 these cells is readily perforated while the density of the protoplasmic contents 

 and the presence of nutritive substances probably furnish a chemotropic at- 

 traction upon the hyphae. I have not observed any case where the hyphae en- 

 tered the thiek-walled exodermal cells direct, but numerous cases have been seen 

 wlffire the passage cells were penetrated, and branches entered the other exo- 

 dermal cells through their thin radial walls, in association with the passage- 

 cells. The hyphae seldom branch until they enter the cells of the cortex just 

 within. When they enter an exodermal cell from the passage-cell they take the 

 shortest coui-se through the base of the cell into the cortex (Text-fig. 12). 



Within the exodermis there is a broad zone of large rounded or oval-shaped 



-A group of cells of the cortex of root showing the coiled 



mycelium in some, and the early infection of others 



(x 167). 

 Text-fig. 3. — A group of cells of cortex showing a partial disintegration 



of the central hyphae of the endophyte (x 167). 

 Text-fig. 4.— Three host cells with disorganizing hyphae (x 167). 

 Text-fig. 5. — The growth of the hyphae towards the nucleus of the 



cell is shown in this figure (x 167). 

 Text-fig. 6. — Cell of cortex showing fungal mass which is undergoing 



digestion (x 167). 



cells, which have thin cellulose walls, comparatively large nuclei, and are separated 

 from each other by large intercellular spaces. Many of the cells of this zone 

 have raphide-crystals, and starch occurs in practically all cells. Large numbers 



