Kelley — 98 — Mycotrophy 



scribed infection in rootstocks of Monotropa; Oliver (1890), in 

 Sarcodes; MacDougal (1900), in Pterospora; and Pfeiffer (1914), 

 in Thismia. An endophyte was discovered in an orchid rhizome by 

 Link in 1840; while an early student of orchid mycorrhizomes was 

 Prillieux (1856), who took his historical introduction back to 

 Tragus of 1552, confirmed Schacht that threads penetrating tubers 

 of Neottia are fungal hyphae ; and stated that at St. Germain he had 

 found sand grains agglutinated in a mass about the orchid. Within 

 the rhizome the 2-3 outermost cortical cell layers were filled with a 

 yellowish-brown material (a material which he found in a great many 

 genera) and the cells containing this material retain their nuclei. 

 These nuclei became very large and often had two nucleoli. The cells 

 having the brown matter regularly contained filaments wound without 

 order about the central mass in the cell ; and not infrequently the fila- 

 ments branched and penetrated through the cell-wall into another 

 cell. After a time this matter diminished in amount, from which fact 

 it may be inferred (said Prillieux) that it serves for nutrition of 

 the plant. Recall that this description was written 29 years before 

 publication of Frank's epochal paper. 



Pfeiffer (1877) confirmed this report for Neottia, finding fungal 

 infection constant and supposing that the fungus takes the place of 

 root hairs which the orchid lacks. A most detailed study of this same 

 orchid was made by Werner Magnus (1900) : he found 3-4 of the 

 outermost cortical layers of cells infected, — sometimes even 6 layers. 

 In this paper Magnus distinguished between "host" and "digestion" 

 cells. In the host-cell the fungus never degenerates : "The cells here 

 pictured, which always possess that ring of thick-walled hyphae with 

 various modifications and the coil of fine median hyphae, — these cells 

 in which the fungus does not degenerate but remains living to the 

 last, shall be designated henceforth as host-cells (Pilzwirthzellen)" 

 (p. 216). Thick-walled hyphae run ring-formed, in various modifica- 

 tions out to the cell-wall and send out fine, thin-walled haustorial 

 hyphae which gain control of the whole cell, — haustoria which seem 

 fitted for passage of nutrient. These cortical ring-like hyphae remain 

 alive after death of the root. 



In contrast tO' the host-cell region, in the digestive region the 

 fungus always degenerates. Thin-walled, protoplasm-rich hyphae 

 grow through the cells in thick coils but very soon die ; or after they 

 have formed protein (as Eiweisshyphen) their content is taken up by 

 the cell and the residue is pressed together while at the same place or 

 at a place mostly lying in the middle of the cell a clotting formation 

 takes place, which results in their separation with a portion of the 

 plant plasm as a clot, which is a dead unchangeable waste product con- 



