Kelley — 174 — Mycotrophy 



cellular digestion of hyphae is exhibited with a clarity unusual in tree 

 mycorrhizae. 



Endrigkeit (1937) says that at no time is there intracellular 

 digestion in Pinus. In the monograph on mycotrophy in Pinus 

 (Hatch, 1937), we learn nothing of the method of intake of nutrient, 

 the mechanism of intake, or of possible phytophagy. 



Limitation of Endophyte: — Confinement of the endophyte to 

 a certain region of the mycorrhiza is a common observation. It was 

 the basis of the early distinction between ecto- and endotrophic my- 

 corhizae, the former having the endophyte supposedly confined to the 

 epidermis of the host. In those mycorrhizae in which hyphae pene- 

 trate internally, Frank (1885) observed that they never go beyond 

 the innermost cortex of cupulifers that are invaded. In fruit-trees 

 the hyphae penetrate three-fourths of the distance through the cortex 

 (BouLET, 1910). In Olea the "prosporidi" are localized in an inter- 

 nal zone of large cells of cortical parenchyma (Petri, 1908). Mc- 

 DouGALL (1914), in studying forest trees of Illinois, found that the 

 central cylinder is never invaded ; while Taxus in France is said 

 (Prat, 1926) to keep the fungus out of stelar tissues by a layer of 

 "tannin" in the endodermis. In Eucalyptus the fungus is found in 

 epidermis and outer cortex but rarely deeper (Smith & Pope, 1934). 

 Of particular interest, remarked Noell (1910), are cases like Cun- 

 ninghamia in which hyphae penetrate only a few certain cell-layers 

 without any reason being apparent why they should not invade all 

 the cortical cells. Even the fossil tree, Ainyelon, shows the central 

 cylinder never penetrated (Halket, 1930). 



Such phenomena were freely recorded by Janse (1897), whose 

 work is characterized by so much admirable detail : In Ophioderma, 

 sporangioles are found in third layer of cortex only while in Lecan- 

 orchis it is the second layer that is invaded, and in Dendrobium all 

 layers except the last are penetrated. In Burmannia the layer next 

 the endodermis is exempt while in Aronychia the hyphae never invade 

 the innermost cortical cells, which are filled with "tannin". In Elaeo- 

 carpus, invasion is to the mediocortex only while in Michelia invasion 

 is confined to certain points in the cortex, and resin canals are never 

 penetrated. So, too, in Dysoxylon the secretory canals are never 

 invaded. 



Limitation in Orchids and other Herbs: — Besides the orchids 

 named by Janse, the following may be cited: In Ccntrosis it is the 

 mid-cortex to which the endophyte penetrates and the inner cortex 

 and the central cylinder are always free from infestation (Arcu- 



