130 MIOCENE CLIMATE. 



it precedes that tree by more than a month. But we have 

 already mentioned that, on a slab from the Schrotzburg, male 

 flowers of the poplar lie besides plane-leaves, which never appear 

 before the flowers. We learn also, by the comparison of the 

 leaves lying on the same slab*, that the hornbeams were already 

 in leaf at the flowering-time of the willows and poplars, and 

 therefore at the end of March (whilst at the present day in 

 Switzerland they only acquire their leaves in the middle of 

 May) ; and from the evidence of the Miocene slabs the liquid- 

 ambars, the elms, and the narrow-leaved maple also bore 

 perfectly developed leaves at the same time with hornbeams 

 and with the flowers of willows and poplars. Thus trees with 

 deciduous foliage, in Miocene times, developed their leaves as 

 they now do in warmer zones, about a month or six weeks earlier 

 than in the modern Swiss climate. We know already that at 

 the time of the Upper Miocene the evergreen trees and shrubs 

 formed nearly half the total number ; but at the same time the 

 woody plants with deciduous foliage also retained their green 

 mantle considerably longer than do their allies in the existing 

 Swiss flora, and a much milder climate was indicated by the 

 flowering and foliation of the deciduous trees at the same 

 time. 



The warmth of the climate is also proved from the occurrence 

 of certain fruits. The fleshy fruits of the laurels are soon de- 

 stroyed when they are exposed to the influence of the weather. 

 We find, however, the fruit and leaves of a cinnamon-tree close 

 beside catkins of the poplar ; they were therefore imbedded in 

 the spring; and the cinnamon consequently probably bore ripe 



* These relations are discussed in more detail in Prof. Heer's work 'On the 

 Flora and Climate of the Tertiary district ' (pp. 59 et seqq.). In these in- 

 vestigations it must not be forgotten that the autumn-falling leaves of many 

 trees (such as the beeches) remain well preserved for a long time on the 

 ground, whilst others (such as those of the maple) soon decay. The former 

 may consequently be easily swept down by water in the spring ; and then it 

 is often impossible to distinguish between the spring and autumn leaves. 

 But if the leaves are still attached to the twigs, if they are not quite mature, 

 or if, being divided into lobes and teeth, they are spread out and well pre- 

 served, we may assume that they were imbedded soon after their fall. 



