Kelley — 176 — Mycotrophy 



(1922) said that the fungus occurs in a definite zone along the ventral 

 midrib of Pellia and that the hepatic seems to exercise control over 

 the fungus. According to Magrou (1925) the fungus degenerates 

 about the archegonia and sporogonia, which seem to exert an inhibitory 

 influence upon growth. Auret (1930) found further that the 

 endophyte does not penetrate gemma-cups and archegonia of Liinu- 

 laria. Moreover, in Seivardiella (Chalaud, 1932) the fungus is 

 checked by active meristematic cells and the bulb is immune. 



Limitation in Root Apices: — From all published accounts the 

 mycorrhizal apex is free from infection. To give some examples : 

 No hyphae were found in the vegetative point of Hippophae (Arcu- 

 LARius, 1928) ; the root tip of Vitis is never invaded (Petri, 1907), 

 nor the apical meristem of Taxus (Prat, 1934) ; while in pecan only 

 occasionally does the fungus enter cells of the growing tip (Wood- 

 ROOF, 1933), In Neottia the fungus is always found a short distance 

 back of the growing point (Drude, 1873), while in Philesia the 

 fungus penetrates tO' within 10-12 zone cells behind the apex (Mac- 

 farlane, 1897). Young roots of Paris are fungus-free 1.5 cm. from 

 the root-apex (Schlicht, 1889). In Monotropa the fungus 

 diminishes toward the apex (Kamienski, 1884) ; it does not enter 

 the meristematic zone of Dipodium (McLuckie, 1922) ; and the root- 

 tip of Thismia is fungus-free (Pfeiffer, 1914). The fungus is sel- 

 dom closer than 3-4 mm. of the root-tip of Corallorhiza (Thomas, 

 1893) ; in Angiopteris and other ferns the endophyte is absent from 

 the root-tip (West, 1917). 



Limitation in Long Roots : — It is well-known that the long roots 

 of extension are fungus-free. Thus Gibelli (1883) said that in 

 Castanea the long, rapidly growing roots are free from infection, while 

 in Cacao the long roots are specifically stated by Pyke (1935) to be 

 fungus-free, and they are rarely infected in Taxus (Prat, 1926). 



Limitation in Green Tissues: — Magrou (1925) noticed that 

 when hyphae invade cells of Pellia containing chlorophyll, the latter 

 is destroyed; and Ridler (1922) also observed that chloroplasts dis- 

 appear in Pellia on fungal invasion. Conversely, where chloroplasts 

 exist there are no fungi: Thus, Bolleter (1905) found that green 

 plants of Conocephalus showed no infection while neither starch nor 

 chlorophyll bodies occurred in infested cells. Again, in Lunidaria, 

 chlorophyll tissue is never invaded (Emberger, 1924) ; and indeed, 

 GoLENKiN (1902) had said that in liverworts infested cells never 

 contain starch or chlorophyll. Moreover, where Orchis incarnata roots 



