118 Transactions. — Botany. 



icy bondage, the soil capable of supporting vegetable life would 

 demand forms suitable to its varying condition. To supply 

 this demand there would be the scanty remnants of the ter- 

 tiary flora before referred to — for Em-ope, cut off from the 

 warmer regions of Africa by the waters of the Mediterranean, 

 would be more dependent on these resources than if it were 

 a portion of an uninterrupted mass of land stretching south- 

 ward to the torrid zone. 



When commenting on the unavoidable destruction of the 

 tertiary species by the glacial cold, I pointed out that deci- 

 duous trees would probably form a conspicuous feature in the 

 surviving remnant. Another peculiarity of this remnant would 

 be the preponderance of herbaceous plants ; for wherever we 

 observe the effects of a low temperature, whether in high 

 altitudes or high latitudes, we find a larger number of her- 

 baceous than arborescent species. 



As Europe, when the glacial cold was at its height, lay 

 entirely within the colder regions of the earth, we may fairly 

 conclude that this was one of the characteristics of its vege- 

 tation. 



If we now suppose the European continent, as its climate 

 gradually improved, to be reclothed with vegetation by its 

 glacial flora, through a mere multiplication of the individual 

 plants, we can readily imagine how monotonous would be the 

 effect. But such a result would be impossible, for in so diver- 

 sified a region, and with constantly changing climatic condi- 

 tions, expansion could not take place without giving rise to 

 variation. New varieties and species would thus appear, the 

 flora being thereby enriched in forms specifically distinct, but 

 belonging to a few generic and ordinal types. 



Eeturning to the British flora, we can now see how the 

 various points in which it differs from the corresponding 

 southern flora— the prevalence of deciduous trees, the prepon- 

 derance of herbaceous plants, and the comparatively few orders 

 represented — seem capable of explanation by the effects of the 

 glacial cold. 



If the prevalence of deciduous trees in the north tempe- 

 rate zone is the result of certain former climatic conditions, it 

 necessarily follows that the vegetation of the southern zone 

 has not been subjected to similar conditions. 



To what, then, must we refer the evidence of ice-action in 

 parts of these islands where light falls of snow now rarely 

 occur ? 



To this question I shall not venture a reply, not having a 

 sufficient knowledge of the geology of the southern hemi- 

 sphere. I may, however, state that the glacial moraines of 

 the Wairau Valley before mentioned might be accounted for 

 by a former elevation of the land. That the land throughout 



