420 JOURNAL OF THE EOYAL HORTICULTURAL SOCIETY. 



And the temperature at 



Edinburgh 56° N.L. is 37° in January 



Bergen (Norway) 00 „ 32 



Yakutsk G2 „ -36 



In the latter group of places we see the great contrast between the 

 temperature of an inland site, such as Y T akutsk, and that of the maritime 

 coast of the west of Europe, which is swept by warm currents. 



Now, the most obvious effect that such differences of temperature have 

 on plants is that a continental climate is favourable to annuals and a 

 maritime to perennials ; for in places where a summer temperature rises 

 high, plants whose whole life-history is comprised in a few months, 

 or even weeks, may easily, therefore, survive ; while the intensely cold 

 winters of the same place would annihilate many perennials that would 

 flourish in a less rigorous climate. Hence evergreen shrubs of South 

 Europe, such as the laurustinus and bay laurel, will survive our winters, 

 which are rarely excessive ; yet the climate in summer and autumn is quite 

 insufficient in its degree of heat to ripen efficiently the grape or Indian 

 corn ; for the summers are as equally tempered as the winters. 



The British flora, as might, therefore, be expected, contains a large 

 number of perennials, especially herbaceous ones. Many annuals, being 

 weeds of cultivation only, would be probably more or less exterminated 

 if our arable land should cease to be cultivated. 



There are no forms peculiar to Great Britain whatever ; with the 

 exception of Eriocaulon septangulare every plant may be found on the 

 Continent, or introduced and naturalised. 



Although our British plants are almost all European, yet they are not 

 equally or at all uniformly distributed over our territory. They have, 

 consequently, been divided into sub-floras, or florulac, each being more or 

 less restricted in area. We are indebted mainly to the labours of the 

 late Professor Edward Forbes and Mr. H. C. Watson for tracing out these 

 districts. The following is a comparative table of the respective results 

 of these eminent botanists, with their nomenclatures : — 



Watson's. Forbes'. 



1. British corresponds with 



2. English „ ■ Germanic. IV. 



3. Scottish „ 



4. Highland „ Alpine. III. 



5. Germanic (in part) „ Kentish. IV. 



6. Atlantic „ 



7. Local or doubtful. 



I Asturian. L 

 Armorican. II. 



That entitled Germanic by Forbes is so called because it is identical with 

 the German flora, though the latter contains many plants wanting in. 

 England. This is subdivided by Watson into (1) the British, which 

 includes plants found in all his eighteen " provinces " ; (2) the English, 

 which includes plants found chiefly in England and not in Scotland ; 

 and (3) the Scottish, embracing plants found chiefly in Scotland and the 



