44 



Porritt : Lype phceopa in Yorkshire. 



barren spots, not because they prefer them, but because they 

 find these places unoccupied, and because they know that they 

 will not there be troubled with undesired company. 



The hig-h mountains offered a natural retreat to these hunted 

 Arctic plants, and they have provided them with a permanent 

 refuge, for here both soil and climate are alike suited to them 

 and intolerable to their enemies ; but the occupation would be 

 o-radual. They would at first attempt to hold the lower heig-hts 

 and all waste and rocky ground, until one after another of their 

 fortresses were isolated and surrounded and the g-arrisons put 

 to the sword. Perhaps we may regard the Dryas on Arncliffe 

 Clowder and the Cornus suecica at the Hole of Horcum as 

 survivors of such garrisons. 



It seems, however, possible that those plants which took 

 refuge on the sea-cliffs and sea-shores might have some chance 

 of preserving their existence. The enemy was at any rate only 

 on one side of them. It would be a weaker enemy, too. Tlie 

 whole horde of the invaders would not follow them, for com- 

 paratively few plants are able to support the exposure and the 

 briny atmosphere of the neighbourhood of the sea. It is true 

 that the numbers of the pursued would be reduced by the 

 climate quite as much as those of the pursuers ; but is it not 

 likely that some of these Arctic fugitives, who were not so nice 

 about the climate, would find themselves on more equal terms 

 with their foes, so that they would be able to make peace witli 

 them and agree to live together side by side ? 



This is, however, no more than a conjecture and a sug- 

 gestion. The only resemblance that I can trace between 

 mountains and the sea-coast as a home for plants, is that they 

 are the two points of the earth where erosion and denudation 

 are the most active, and where fresh land-surface is continually 

 being laid bare. The crumbling cliffs, and the changing sands 

 and mudbanks of the seashore may compare with the rock- 

 falls, and talus-slopes, and torrent-detritus of the high 

 mountains. Both are alike in possessing waste unoccupied 

 ground where plant-competition is at its lowest. 



TRICHOPTERA. 

 Lype phaeopa in Yorkshire.- — This little trichopteron, which 

 seems to be hitherto unrecorded for Yorkshire, I have had — 

 taken by myself at Castle Howard — ever since June 1896. — 

 Geo. T. Porritt, Huddersfield, 9th January 1905. 



Naturalist, 



