Monotropaceae with Reference to Ericaceae 59 



cells — in fact the epidermal cells in M. hypopitys are smaller 

 than those of the layer beneath. MacDougal and Lloyd (50) 

 report the presence of starch in the cortex of the roots of Mono- 

 tropa near the tip, though the material examined by the writer 

 failed to show this. According to Kamienski, secondary roots 

 arise endogenously as in the Pyrolaceae. 



The root tip of M. uniflora (Fig. 1,4) is quite similar to that 

 of M. hypopitys, except that at the apex the regions of growth 

 are even less distinguishable; the pseudoparenchyma between 

 the walls appears to be better developed; and the outer layer 

 of the sheath formed by the intertwining hyphae does not thin 

 out over the apex as in M. hypopitys, but continues as a layer 

 of the same thickness completely around the root tip. This 

 has been described and figured by MacDougal and Lloyd (50) 

 (p. 10, PI. 11). The root cap consists of one to three 

 (MacDougal and Lloyd 1-4) layers of flattened cells filled with 

 deeply staining material. The cells appeared crushed in all of 

 the root tips examined. The area which the root cap covers is 

 exceedingly limited. MacDougal and Lloyd have figured all 

 stages of the penetration and development of the fungus in the 

 epidermal cells. The nucleus becomes deformed; the hyphae 

 form grape-like clusters, which they consider to be atrophied 

 reproductive branches. They also state that starch grains 

 occur in the outermost layer of the cortex and that secondary 

 roots arise from the third layer of the cortex. 



Oliver (58) has described and figured the root tip of Sarcodes 

 sanguinea Torr. The appearance is very like that of Monotropa 

 uniflora. In Sarcodes the root cap is better developed. Oliver 

 figures five layers. The fungus surrounds each epidermal cell, 

 and forms a sheath of hyphae on the surface. He states that 

 the hyphae never penetrate the epidermal cells, but he also 

 mentions that the nuclei of the epidermal cells are modified into 

 rod-like structures. MacDougal and Lloyd mention the pres- 

 ence of the mantle of mycelium that extends completely around 

 the root tip; that this is composed of two regions as in Mono- 

 tropa and that the hyphae penetrate the epidermal cells. In 

 the layer beneath the epidermis Oliver figures a few starch 

 grains. He reports that secondary roots arise exogenously. 



MacDougal (48) in "Symbiotic Saprophytism" and Mac- 

 Dougal and Lloyd (50) have described the root tip of Ptero- 



