Lancaster. — The Fungi of New Zeahntd Epiphi/fir Orehufs. 189 



higher plants and a fungal mycelium the name " mycorhiza " is given. 

 Mycorhizae are of two kinds — those in which the fungal elements do not 

 penetrate the root, but merely form a dense mat round it, and those in which 

 the hyphac enter the root and form coils within its cells. There can be no 

 doubt that the relationship existing between the roots of our epiphytic 

 orchids and the fungal filaments comes under the head of mycorhizic asso- 

 ciations. It is evident, moreover, that the mycorhizae in their case arc 

 endotropliic. Orchids seem to be particularly prone to the formation of 

 such alliances, and it is therefore not surprising to find that some New Zea- 

 land orchids possess mycorhizae. Among mycorhizae hitherto described 

 is that of a British saprophytic orchid, Corallorhiza innata, which was 

 dealt with by Messrs. Hanna and Jennings in a paper published in the 

 •■' Proceedings of the Koyal Dublin Society " (1898). 



There is little fixity of opinion as to the exact nature of the benefits 

 accruing" to the partners in these mycorhizic associations. The view of 

 Hanna and Jennings with regard to Corallorhiza is that the hairs found on 

 the rhizome of the plant are produced with the object of attracting thi' 

 fungal hyphae into the rhizome, so that the orchid can use them to augment 

 its supply of food-materials. According to these authorities, the coils of 

 hyphae in the orchid's cells are gradually absorbed as food by the proto- 

 plasm, starch-grains appearing in abundance as the hyphae disappear. A 

 view held by Groom and Janse with regard to endotrophic mycorhizae in 

 general is that the fungus is digested by the root, thereby supplying com- 

 bined nitrogen. Other investigators — c/., Hiltner and Magnus — hold 

 .similar views. 



In the case of the New Zealand orchids it is not j)robable that the hairs 

 on their roots are produced as fungus-trapping organs. In some cases it 

 is certain from the manner in which the hyphae branch that they are leaving, 

 and not entering, the root. In many instances spores have been seen in the 

 hairs, and in more than one case the cavity of a hair at its extremity was 

 observed to be densely packed with spores. \Vliat seems more probable is 

 that the hairs perform, for a time at least, the functions which root-hairs 

 perform in ordinary terrestrial plants — viz., absorption of water and mineral 

 food. As above mentioned, the velamen at maturity is a dead tissue : its 

 cells after having thickened their walls in a curiously intricate fashion lose 

 their living contents, so that the hairs springing from them must also die, 

 and presumably become functionless. It seems probable that no special 

 significance is to be attached to the presence of the hyphae in the hairs. 

 That the fungi sometimes use them as a means of entering the root cannot 

 be doubted, but it is very likely that the hyphae are capable of penetrating 

 the velamen at almost any point, and that their chief mode of entrance is by 

 direct penetration of the outer cells of that tissue. 



It is well known that humus is invariably penetrated in all directions 

 by the hyphae of many species of fungi, and these are believed to assist in 

 l)reaking down the complex organic compounds of the humus, thereby 

 bringing a large amount of plant-food into an available condition. The 

 humus, from which these epiphytic orchids must obtain practically all 

 their food-materials except carbon, is formed, as before stated, largely by 

 the decay of lower plants, chiefly lichens and mosses. It is unlikely that 

 the carbon of the humus is utilized by the orchids, as they are all well 

 supplied with chlorophyll, and it would therefore seem that their supply 

 of carbon from atmospheric sources would be adequate to their needs. It 

 cannot be said that their supply of available nitrogen is by any means 



