LIFE OF AN ORCHID 



2-1 



of the protocorm, and the fungal filaments pass in and out through them. The cells 

 near the suspensor are attacked, but the parasitic fungus is prevented from invading 

 the whole plant by the latter's power of digesting it. The nuclei of the ceUs swelf, 

 put out pseudopodia (extensions hke a glove-finger) which enclose the fungus' 

 reducing it to a dead amorphous mass, which seems finally to disappear.' The growing 

 hypha; (filaments) of the fungus form coHs (Text-fig. 4, II) or balls^ within the ceUs 

 which are invaded by degrees, coils being formed in each cell before passing on to 

 the next. The fungus only attacks cells almost fuUy developed, and those invaded 

 no longer grow perceptibly. There is no growing point in the infected area. Cells 

 containing chlorophyll, tannin, mucus, raphides and other crystals are never invaded.' 

 The meristematic cells (nascent or very young tissue) are never entered, the only 

 ceUs infected still capable of growth by division being those of the seed, where the 

 first entry is made.' The hyphas do not as a rule extend from the seed to the root, 



the latter becoming later invaded from the soil through the root-hairs. In Neottia, 



however, the fungus passes from the 



protocorm into the rhizome and infects 



the successive roots (Text-fig. 5, III). 



The digesting cells are recognisable by 



the degenerating mass which more than 



half fills them. I 



Reissek (1846) first recognised the 



fungal nature of the coils, and was fol- ^S^^Ms^J ^i^^^f^-JBJ'^Mt 



lowed by Irmisch, Fabre, Wahrhch (who \^f If^^^ ^^p- 6\^sJ^ 



proved their presence in 500 exotic " ' ~~^ 



species), Chodat, Ramsbottom and i m: 



many other observers, but it is to Noel '^^^'■'^S- 5- I- Seed of NeoUia showing oval embryo already 

 ■pi, 1 , , , invaded by fungal filaments. II. Protocorm of NeoUia. 



ISernara S researches that we are largely Dotted area shows region penetrated by fungus. III. Plant 



indebted for our nresentknnwIpHap Hie pf^'^'"''''^'* young flowering axis. Area infected indicated 

 mucuiCU lOr our present knowledge. His by dots. From Noel Bernard's "fitudes sur la tuberisation" 



"Etudes sur la tuberisation" (looz) ^^""^ s^"^>'^^^ '^e B<>'^"'i"e, ^y (1901), by kind petmission of 



1 111 1 ^ ^ >' ^ the editor. 



showed that the seeds of orchids can only 



germinate in the presence of the fungus, and that the seedling is infested in its earliest 

 stages. He isolated the fungus from the orchid root and grew it on nutrient media, 

 and showed that orcliid seeds would germinate without difficulty if the appropriate 

 fungus was supphed. His great work, "L'evolution dans la symbiose" (Ama/es 

 des Sciences nat. ser. 9, ix, 196), appeared in 1909, and in the same year Burgeff's com- 

 prehensive work. Die Wmxelpil^e der Orchideen, saw the light. These researches 



'Ramsbottom, Orchid Mjcorrhi^a (Charlesworth & Co.'s Catalogue, 1922), reprinted in Trans, 

 lint. Mycol. Soc. viii, 28 (1922). ■> / r 



'Pi. A, fig. 3, if properly focused, shows the fungus filaments with baU-Uke spores and the large 

 nucleus floaung m the midst of the ceU, taken from a rhizome of Epipogon aphjllum (p. 6). 



4-2 



