OKCHIS ELODES 307 



sponding one in maculata, though it may be argued that these are 

 more differences of degree than of kind, and lie within the range of 

 possible variation. Though individually not of decisive importance, 

 they are co-ordinated to form a whole which is remarkably constant. 

 They are not found with varying changes and permutations, but are 

 closely correlated. Each item may be small, but the sum total is 

 considerable. I am inclined to think, however, that no conclusive 

 argument, either for or against specific identity, can be drawn from 

 a comparison of the two plants. 



The evidence furnished by their distribution in Britain does not 

 appear to have been sufficiently considered. Maculata grows on stiff 

 basic soils in woods, fields, etc., and on chalk downs, attains its greatest 

 perfection in a cool rich loam, and is mainly a lowland plant. Elodes 

 grows on heath-land, on the peat, frequently in boggy ground amongst 

 sphagnum. Webster found colonies of it killed outright through 

 drainage. Dr. Stephenson tells me that elodes is very plentiful in 

 the island of Arran from sea-level up to highland bogs, but maculata 

 is confined to the lower levels. Each species occupies large areas in 

 Britain from wdiich the other is entirely absent, showing that the 

 habitat of the one is unsuitable to the other. In a few limited areas 

 they are found together, but this is rare, and is probably due to the 

 soil-conditions necessary for each overlapping in these very restricted 

 localities. Under such conditions hybrids occur, but Dr. Stephenson 

 says that in Arran, where they grew together in places, they very 

 seldom seemed to cross. Ascherson and Graebner state (Syn. iii. 

 748) that elodes is very difficult to grow, easily dying off, and re- 

 senting any change of environment or conditions of growth, but, 

 nevertheless, shows great constancy under cultivation. 



If maculata and elodes grew freely together over large areas, it 

 might be argued that the differences between them are not so great 

 that they cannot be explained by variation ; but, since each occupies 

 large areas from which the other is absent, it is evident that there is 

 some inherent difference of a -deeper kind. If elodes is a mere variety 

 of maculata, why does it not arise in the areas where maculata is 

 abundant ? A variety must necessarily arise in the neighbourhood 

 of the mother-species, and fairness compels us to admit that the soil 

 which is favourable to the parent-plant should be equally so to its 

 varietal offspring. It seems improbable that a plant should give rise 

 to a variety which cannot exist on its parent soil, and the complete 

 absence of elodes from large areas where maculata is prevalent shows 

 that it cannot establish itself under the conditions favourable to the 

 latter. 



If it be suggested that seeds of maculata were blown on to 

 heath-land, grew there, and became gradually modified into elodes, 

 this easy solution involves many difficulties. Maculata cannot grow 

 on heath-land, or at least cannot maintain itself there, for how else 

 can the complete absence of our commonest and most prolific orchid 

 from the areas occupied by elodes be explained ? The first seeds 

 germinating in the new habitat would be pure maculata (for a certain 

 time must be necessary for the new environment to take effect) and 

 would have a hard struggle against adverse conditions, which they 



y 2 



