74 The hish Naturalist. March, 



But despite this reverse, let us "in the interests of science," pursue the 

 matter, aud see whither the next step in the hypothesis will lead us. 

 Assuming, for the sake of argument, that grain from, say Northern Italy, 

 where the plant does grow, had at some time been imported, it surelj' 

 requires an elastic imagination to conceive how the seed of a plant which 

 affects such a habitat as Glyceria festiiccBforniis is likely to become mixed 

 with cereals. The bulk of distillery and corn-mill aliens are weeds of 

 cultivated or waste ground — Melilots, Medicks, Sisymbriums, Silenes, 

 and a hundred more — and plants of other situations, such as sea-shores, 

 or marshes, or woods, are generally conspicuous only by their absence. 

 An examination of the Comber casuals shows that they are no exception 

 to this rule. 



Would it be rational to doubt that Scirpus h-iqueter is native on the 

 Shannon estuary, because it could be shown that one of the Limerick 

 flour-mills had, at some time or other, used wheat that came from the 

 South of England ? Yet the Limerick casuals are legion, several of them 

 have established themselves, and S, triqtieter grows almost within a stone- 

 throw of some of these. 



Then further. Having, by some strange chance, got the seeds of our 

 maritime grass (they are not particularly light seeds, nor gifted with any 

 special means of dispersal) mixed with our foreign grain, and that grain 

 duly transported to Comber, and the seeds safely launched thence into the 

 river, how comes it that, though capable even as a recent immigrant of 

 forming an extensive colony across eight miles of sea— a remarkable 

 feat — the plant has not established itself about the Comber River, where 

 the ground is suitable, and where there must have been a hundred seeds 

 floating for one which reached its distant actual station ? Yet G. festti- 

 ccrformis has never been detected in that well -worked ground. Could it 

 even be shown that any one of the Comber aliens has spread down the 

 river and established itself, this at least would be a straw to which we 

 might cling. But even this collateral evidence is not forthcoming. I 

 need not pursue the matter further. Of course it may be argued that 

 plants do spread to unexpected places, and that we cannot prophecy the 

 range even of an alien from the known facts of its introduction. Quite 

 so. But in the present case, the fraction representing the probability 

 of each step in the hypothesis is so small, that the product is a fraction 

 which is for practical purposes insignificant. 



Not only in our distilleries aud flour-mills, but in stores, and indeed in 

 every grocer's shop and hen-run over the country, foreign grain is to be 

 found. It is little exaggeration to say that seeds of foreign plants rain 

 down year by year all over our islands, and this it is that makes the work 

 of the field botanist now-a-days so difficult ; but, unless built on some 

 foundation of fact, and supported by buttresses of probability, a hypo- 

 thesis raised on this circumstance alone will not stand. Could Canon 

 Lett — who, by the way, does not say that he has studied either the plant, 

 or its Irish habitat, or the Comber casuals — put forward a connected 

 argument such as Mr. Colgan {/ournal of Botany, xxxii., 104. 1894) 

 introduced in connection with Prof. Areshoug's plea in favour of 



