Kelley 



— 166 — 



Mycotrophy 



water was excreted : a hypha being drawn into the drop would be 

 prevented by surface tension from growing out of it again, and 

 would thus continue its growth by coiling within the water drop. 

 Perhaps something of the sort occurs in orchid cells, those cortical 

 cells nearer to the central cylinder having an higher concentration of 

 ions in the cytolymph and accordingly a greater surface tension in 

 the protoplast. Regardless of explanation, the hypha coils in cells 

 of the cortex, the nucleus of the cell remaining intact but becoming 

 enlarged, hypertrophied and even dividing amitotically. According 

 to most authors, hyphae never penetrate raphide cells but Busich 

 (1913) says that the fungus is not warded off by calcium oxalate but 

 on the contrary forms it. 



Later the hyphal coils degenerate and release their content into 

 the host-cell. "As with many other orchids, the process of ingestion 

 of the hyphal coils is preceded by a turning point at which the h.i.c. 



Fig. 12. — Portion of a cross-section of the ectendotrophic 

 mycorrhiza of Cornus jlorida, showing hyphal coils or 

 pelotons (p) and vesicles (v). 



of the hyphal clumps reached a maximum of /'H 6.2." (Hamada, 

 1939). The actual breaking down of the hypha seems due to the 

 action of a proteolytic enzyme (Burges, 1939) and results in the 

 formation of a more or less homogeneous yellowish mass in the 

 centre of the host-cell. This is the "yellow body" or "matiere 

 brunatre" or "gelbliche Stoffe" of earlier investigators. The yellow 



