88 



IMIOCKEDTNQS OF Tllli; 



'I'hyimis Serpvlliiiii, Linn. Sparganiiim ramosura, Huch. 



Ruiiicx crisptis, Linn. Potamogoton rufescens, Schrad. 



Atriplcx prittila, TAnn. Caivx dioica, Linn. 



Quercus Robiir, Tjinn. \ Anthoxantliiim odoratiim, LAnn. 



Coryliis Avcllana, lAnn. riiragiuites coiuinunis, Trin. 



Almis gliitiiiosa, Linn. Poa trivialis, Linn. 



Bet Ilia nana, Linn. 



Through the post-glacial ages tlie vegetation of our islands 

 became richer tlirough the transport, by water and air-currents 

 and by birds, of additional species. At no time can it be said 

 that this influx has stopped. In a flora entirely derived from 

 nearer or more remote lands we must include all plants which 

 have reached our shores, whether early during the ice age, in the 

 ages intervening, or quite recently in our own day, if such 

 additions are independent of human agency. 



The existence of the American JEriocaulon septangulare. With., 

 on the western coasts of Scotland and Ireland — the only member 

 of an exti'a-Europeau order which is found nowhere else in 

 Europe — is no doubt due to the agency of some American bird. 

 It is included in our native flora as Anacliaris Alsinastrum, Bab., 

 should also be, though it has been added to our Flora in our own 

 day. This plant was first observed in County Down about 1836, and 

 made its way to England in 1841. There is no evidence to show 

 and no reason to suppose that its presence in Ireland was due in 

 any way to the agency of man. The occasional occui*reuce of 

 American birds on our sliores is well known, and only a few weeks 

 ago wo had submitted for our examination a specimen of a bittern 

 (Bvtorides virescens) which, having crossed the Atlantic, was shot 

 in Cornwall. Such a visitant might have brought to our shores 

 the seeds of plants like Eriocaulon or Anacliaris. 



The most remarkable case in recent times of the introduction 

 and wide distribution of a plant by wind currents is that of 

 Phytophthora infestans, De Bary. Towards the end of July 1845, 

 this plant was first detected in the Old World in Belgium, and 

 within two months thereafter it had spread itself over England, 

 Scotland, and Ireland, over France, Germany, Denmark, and 

 Kussia, doing serious injury everywhere to the potato crops of 

 these countries. 



Though so recently introduced, the Phytophtliora and the 

 Anacliaris must be reckoned as much members of our indigenous 

 Flora as the others which reached us by agents free from the 

 influence of man during the ages that have intervened since the 

 glacial ice disappeared from our land. 



Various estimates have been made of the centnries that have 

 run their course since the glacial epoch. Beyond the date at 

 which man began to record time we can have no definite inform- 

 ation. AVe can trace the succession of events, but the statement 

 of the time required to bring about these events, being based on 

 deductions from the accompanying or resultant physical or 

 liiological phenomena, must differ according to the estimates of 



