fr> SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE 



however, were not injured in this way ; but notwithstanding the mild winter they 

 only maintained their . improvement of the previous year, without attaining the 

 standard of growth of 1878. The reason of this failure, no doubt, was the 

 unfavourable nature of the previous autumn for the ripening of wood, combined 

 with the ungenial nature of the growing season, both of which were well-marked 

 evils at the Botanic Garden, as I was informed by the late lamented Mr Sadler 

 shortly before his death. 



The evergreens, on the other hand, recovered their loss of the previous 

 year. Apparently the frost of April had not injured them, and they had been 

 stimulated by the mildness of May, as their growth till the end of that month 

 bore a high proportion to the whole annual increase. 



This attempt to connect the annual variations in the increase of wood with 

 temperature, and to explain the curious contrasts between deciduous and 

 evergreen trees in their annual growth by the effects of temperature alone, 

 cannot' be considered as altogether satisfactory. Neither are the difficulties 

 cleared up by considering other causes which must manifestly affect the 

 growth of wood. Violent winds, for example, must be prejudicial not only by 

 tearing down important branches, but by damaging the leaves. Every one 

 must have observed the injury done to foliage by storms, particularly in spring 

 and the beginning of summer. Multitudes of leaves are blown away, and 

 those which remain hang limp and shrivelled from the branches, their petioles 

 twisted by the wind, and the circulation through them thus hindered by bruis- 

 ing of the vessels. In the records of the Scottish Meteorological Society many 

 gales are reported as having occurred at Edinburgh in the years with which 

 we have to do, but I cannot clearly trace a connection between them and any 

 diminution in the growth of wood. I should have expected the greatest 

 damage to have been done in 1881. In the previous year, indeed, there were 

 three gales in May, but it was a backward spring, and the leaves may thus 

 have escaped. At all events we know that Sir Robert remarked the richness 

 and abundance of foliage in June, and there were no gales in that or the sub- 

 sequent growing months. In 1881, on the other hand, one gale in May, three 

 in June, two in July, and four in August were recorded ; yet this was the year 

 in which, with all the disadvantage of a previous winter of almost unprece- 

 dented severity, the growth of deciduous wood made a remarkable rally. But 

 the fact is that the effects of each gale must be watched in order to know 

 whether any general damage has been done to the leaves or not, so much 

 depends on the strength of the wind, its direction, and the shelter which may 

 protect the trees concerned. I should expect that differences between the 

 annual increase of deciduous and evergreen trees might sometimes be due to 

 this cause, as the leaves of the latter, from their shape, cannot be exposed to 



