LIFE OF AN ORCHID 31 



rhizome. The European and American Calypso horealis {bulhosd) has a pseudo-bulb, 

 but in old plants sometimes develops a coralloid rliizome, strongly infected, apparently 

 an effort to supplement insufficient nourishment by increase of absorptive surface 

 and fungal assistance, i It is a sure sign of saprophytism, 



_ Epipogon has a similar coral-like rhizome, which sends out thread-like runners which 

 give rise to fresh rhizomes (PI. 21). It is essentially an underground plant, sometimes 

 growing for several years without appearing above the soil. The leaves are reduced to 

 sheaths without chlorophyll, and the plant is saprophytic. A swelling at the base 

 of the stem forms a large reservoir for the storage of water. It is extraordinary that 

 a plant of such low organisation vegetatively should have evolved such highly 

 organised flowers, wliich have attained a level of perfection equal to that of Orchis. 

 Both it and the preceding have absorbent hairs on the rhizome. It only flowers in 

 very favourable seasons, just often enough to maintain the vigour of the species by 

 cross-pollination. A bunch of small independent rhizomes may sometimes be found 

 at the base of a flowering stem. 



We now come to the highly organised Ophrydeas, in which rhizomes and mono- 

 stehc fungus-infected roots are replaced by tubers. The palmate tubers of Cceloglossum, 

 Gymnadenia and the Dactylorchid group of Orchis form a transition to the rounded 

 entire polysteKc fungus-free tubers of Orchis and Ophrjs, in which, according to 

 Bernard,^ a very diffusible substance3 stops the development of endophytes, though 

 the free tips of paknate tubers often contain mycorrhiza. As a rule only the adventitious 

 roots are infected, Khi^octonia repens being the most common fungus. R. violacea is 

 found in potato tubers. In ling, Calluna vulgaris, a fungus invades the whole plant, 

 and waits in the seed-coat to infect the young seedling.4 



As soon as the flower opens the beautifurand very varied floral mechanisms for 

 automatically attaching the poUinia to visiting insects come into play, and the latter 

 distribute the poUen on the stigmas of flowers, in almost every case growing on 

 separate plants. About ten European species are self-fertilising. It is remarkable^hat 

 they were aU previously organised for the removal of the pollinia by insects, and, with 

 perhaps one exception, have not been always self-fertilising (see Pollination and 

 Fertihsation). In the few European species capable of self-poUination, cross-pollina- 

 tion by msects stiU occasionally occurs. The ripe seed-capsules open by longitudinal 



', ^^T^ "^^ "\- P.P- 5^' 35' 47- ' Bernard, Am. Sc. nat. Bof. p. 221 (1911) 



3 Noel Bernard placed a sterilised fragment of a tubercle of Hi^^anfog/ossumor of an Opjbrys at 



This^ffiL ? 1 ^"/^^^ he sowed Rhzoaoma repels, the fungus which invades the Ophrydes. 

 m^nt of t Ltr^°?F T" "fZ-'^l" ^'r'^ ^'"PP^'^- "^^^ ^°1"'^1^ f^"gi"de substance of?he frag" 

 ks filint .^ ^ ui T^u '^^ ^t^ ^^^ ''°PP"^ '^^ development of the fungus long befofe 

 had nn eff . ^"^^'^ 'v '"^''?''- ^^' ^""^''^'^'^ ^"'^ ^^" '" ^^e case of Rh^zo^ima repens, but 

 had no effect on R. mucoroides, the fungus which invades Vandas. Camus, op. cit.p. 36 (1928) 



