48 Henderson — Comparative Study of Pyrolaceae and 



We see, therefore, how artificial, untrustworthy, and inter- 

 blending these distinctions are. There are also other great 

 resemblances between the Ericaceae and the Pyrolaceae and 

 Monotropaceae. All of the Ericaceae are shrubby rarely arbor- 

 escent, often sub-shrubby. The Pyrolaceae as a whole are sub- 

 shrubby, Chimaphila umbellate often becoming very thick, 

 woody; most of the genus Pyrola is sub-shrubby also, with the 

 exception of Pyrola or Moneses uni flora. The Monotropaceae 

 are essentially saprophytic herbs, but they perennate from 

 underground woody parts. 



Historical 



Owing to the complete historical references on the subject 

 of mycorhiza in general given by Gallaud (22) and Rayner (64), 

 the writer has confined herself to those dealing with mycorhiza 

 in the Ericaceae alone. 



As early as 1842, Rylands (67) investigated the "byssoid" 

 substance on the roots of Monotropa hypopitys and came to the 

 conclusion that it was a fungus living on the roots. In 1856- 

 1865, Chatin (6) described M. hypopitys as a parasitic plant. 

 In 1873, Drude (11) investigated the roots of M. hypopitys, 

 coming to the conclusion that the plant is saprophytic. In 

 1 88 1, Kamienski (38, 39) also described and figured the con- 

 dition in M. hypopitys, and formulated the hypothesis that 

 there existed a symbiosis between the plant and the fungus. 

 During the last thirty-five years, it has been shown that sapro- 

 phytism is widespread throughout the Ericaceae proper. Frank 

 (19), in 1887, described the appearance of ericaceous roots 

 infected by fungi. He mentions particularly the much en- 

 larged epidermal cells, filled with knots of hyphae, the absence 

 of root hairs, and the reduction of the root cap. Those men- 

 tioned as possessing endotrophic mycorhiza are Andromeda 

 polifolia, Vaccinium oxycoccus, V. uliginosum, V. macrocarpum, 

 V. myrtillus, V. vitis-idaea, Ledum palustre, Calluna vulgaris, 

 Rhododendron ponticum, Azalea indica, Empetrum (included by 

 him under Ericaceae). He says, however, that they have not 

 been found in Pyrola and that in Monotropa the mycorhiza is 

 ectotrophic. 



