Jaxuaby, 1902.] 



KNOWLEDGE. 



17 



husbandry banished the sylvan species, and allowed other 

 plants to usurp the ground. And all the time, as trade 

 and intercourse increased, circumstances favoured the 

 introduction of fresh colonists. The growth of towns 

 began to have a local effect on the flora ; accumulations 

 of rubbish of all kinds harboured a motley half-alien 

 voget.ation. and the fouling of rivers tended to break up 

 the natural plant associations of the watei-s. The 

 draining of marsh-lands completely altered the flora of 

 largo areas; the building of roads and the diverting of 

 streams played their parts both in extermination and 

 introduction. The gi'atifying of the a?sthetic perceptions 

 of the race also by degrees exercised a great influence 

 on the flora, and with the advance of horticulture exotic 

 after exotic escaped from the bounds of cultivation and 

 moro or less pemianently won a place among the native 

 vegetation. With the growth of modern commerce, and 

 tho construction of canals and of railroads, an immense 

 impetus was given to the introduction and dissemination 

 of all kinds of plants; till, in these last days, we deem 

 it a matter of but momentan' wonder to find, growing 

 in company with native foniis. some flower that has 

 wandered hither from the shores of the Black Sea or 

 the Baltic, from New Jersey or California. 



From this brief history it will be seen that the 

 vegetation of our islands, as it now presents itself, is 

 by n-^ means a homogeneous or natural assemblage of 

 plants. The higher regions of the mountains, the large 

 lakes, swamps, and bogs still retain their primitive 

 facies, and there the original flora remains almost un- 

 molested ; but as we pass from these waste lands to 

 the inhabited areas, where highly cultivated land is 

 dotted over with towns and villages, and intersected 

 with roads, railways, and canals, a gi-eater and greater 

 number of alien plants put in their appearance, till iu 

 waste ground adjoining harbours or mills, we may find 

 a rank flora struggling for existence amid murk and 

 dust, in which exotic plants, the produce of widely 

 separated lands, fonu the larger portion of the vegeta^ 

 lion. To take an instance, the flora of Ireland numbers 

 about 900 undoubtedlj' native species, to which may 

 be added about 130 others which, though now pemianent 

 members of the flora, are considered to be possibly or 

 certainly introduced originally ; and about 200 other 

 plants liave been found growing spontaneously, which 

 are certainly exotic, and not established. In other 

 words, of this total of 1230 plants, 73 per cent, represent 

 the original vegetation of the country; 10 per cent, we 

 may generally call plants which came with man and 

 have now won a place in the pei-manent flora; while 

 1 7 per cent, represent the waifs and strays brought into 

 the country by trade, agriculture, and horticulture ; 

 some of the last will no doubt eventually establish 

 themselves. 



Wo may now consider in greater detail the various 

 groups of which our immigrant vegetation is composed, 

 and dip, where it is possible, into the history of a few 

 of their leading members. If I draw many of my 

 examples from Ireland, it is because the recent publi- 

 cation of " Irish Topographical Botany " brings detailed 

 statistical information concerning the flora up to a later 

 dato than is available for England. 



First we have the group of crop plants — species which 

 are grown for economic pui-poses, and which may spread 

 and establish themselves. Some of these are, others 

 may be, original natives; others again are undoubtedly 

 exotic. The Lucerne {Mcdicago saliva), for instance, a 

 native of the eastern Mediterranean, has long been 

 grown as a fodder plant, and has now established itself 



on banks and dry gi-ound in many places. The Comfrcy 

 (Sy III [ill Ilium (ifflcinah), on the other hand, is un- 

 doubtedly native in England, but apparently not so in 

 Scotland or Ireland ; yet has been so widely cultivated 

 that its range now extends all over Ireland, and well up 

 into Scotland. The Parsnep {Fai<linaca saliva) in rank 

 and distribution stands on a very similar footing; it has 

 been in cultivation since Roman times. The Turnip, in 

 its various fonns {lirassica Jiapa, Napus campestris) 

 may be cited as one of the plants whose standing it is 

 now almost impossible to determine. It has been widely 

 cultivated for several thousand years, and is so still, 

 whether as a root crop, for fodder, or for the manu- 

 facture of rape or colza oil. Which of the many forms 

 are or were native, and what their distribution was, are 

 questions which cannot now be answered with any degree 

 of satisfaction. 



From these cropplants we turn to the next gi-oup — 

 the many imwelcome species which accompany them iu 

 tilled gi'ouud, and which we call weeds. The typical 

 weeds of cultivation are annual plants with small seeds, 

 and they favour dry soils. Only annual plants (or 

 species with deep-creeping underground stems like the 

 Couch-gi-ass) can maintain their position in tilled land, 

 which each year undergoes a complete turning-over. 

 Their numerous small hard seeds are well calculated to 

 receive a wide scattering by wind or other agencies, to 

 escape the eye of bii'ds and other gleaners, and to 

 eudiu'e the severities of the winter. Abundantly sown, 

 they year by year bring forth abundantly. In a field 

 of com we see these plants at their best. The Poppies 

 may be original natives, but we certainly never see their 

 scarlet blossoms in such glorious display as among the 

 com. The Fumitories belong to the same category. The 

 Corn-Salads ai'e more open to suspicion, except 

 V. olitoria, which may be seen far from cultivation; on 

 the basaltic cliffs of Antrim, it forms a close mat in 

 spring with the Mossy Saxifrage, mixed with several 

 species of Hieracia. The White Mustard (Brassica alba), 

 Wild Radish (Rapliaiim Raphnnistrum), Erysimum 

 rheiranlhoides, the charming Blue-bottle {Cenlaiirea 

 Cyaniis), the Corn-cockle {Lychnis Githago), are confined 

 to cultivated ground, and we assume them to have been 

 introduced with seed. Many of them can maintain 

 themselves year by year if only tillage keep the ground 

 clear of aggi-essive perennials; but others, like Gold-of- 

 pleasure {Camelina saliva), Saponaria Vaccaria, Silene 

 dichotoma, etc., though growing luxuriantly when sown 

 with the crop, do not usually appear the following 

 season ; perhaps the dampness of our island-winters 

 destroys the seed of these plants of the European 

 continent. Of some of these weeds of cultivation, now 

 abundant, we can approximately date the introduction. 

 Veronica Burhaumii. a plant with a wide distribution 

 on the Eurasian continent, appeared in England about 

 1825, in Ireland prior to 1845; it is now one of the 

 common weeds of cultivated ground from end to end 

 of these islands. Veronica pereyrina is an American 

 plant, now widespread over Europe. It appeared in 

 Ireland in 1836, and has colonised garden ground over 

 a lai-ge area of the north-west of the island. Of the 

 Lesser Broom-rape (Orobanclie minor), we read in 1866 

 that it has been noticed in two clover-fields in Cork, 

 for one season only, having been introduced with the 

 seed ; now it occurs over the whole east and south-east 

 of Ireland, from Belfast to Bantrj', and in the south-east 

 is permanently established. So with the Clover Dodder 

 (Cuscula Trifolii) in Ireland. In 1866 it " has been 

 observed once or twice in clover fields, but has not 



