170 Sir Eobert Christison on the 



roots, and carried a fine leafy head. But it Las evidently 

 been severely damaged since, for the trunk made no 

 advance last year, and in October its head was miserably 

 defective in foliage. 



5. The two evergreen oaks were not measured in 1878. 

 In 1879 both made a little progress, but probably less in 

 that unpropitious summer than in average years. In 1880, 

 however, in spite of the fineness of the season, one of 

 them made an increase of only O'lO, while the other 

 grew actually 0*80, or fully twice as much as in the 

 previous year. This difference supports the view that the 

 cause of the general defalcation in the growth of wood in 

 1880 was not merely the want of thorough ripening of the 

 young wood of 1879, but also the intense frosts in December 

 of that year. For the former grew unprotected in the 

 middle of the garden, and, in common with its species 

 generally, lost its evergreen leaves long before the approach 

 of spring ; while the other grew about 30 feet to the south 

 of the Palm House, being thus defended by a lofty heated 

 house from N.E., N., and in some degree N.W. ; and in 

 consequence this tree, alone of all its species in the garden, 

 retained its leaves green and vigorous till they withered 

 and dropped, according to the usual rule, with the develop- 

 ment of new foliage in summer. 



6. Of two specimens of Pinus excelsa, apparently of the 

 same age, growing on the terrace in front of the long line 

 of glass-houses, near one another, and circumstanced in all 

 respects exactly alike, both added rather over a third of an 

 inch to their girth in 1878, and both only a fifth of an inch 

 in 1879. But in 1880, while one was fully clothed with 

 foliage, old and young, and again increased its trunk-girth 

 by a third of an inch, the other showed very thin old 

 foliage, scanty new twigs, and two years' growth of its top- 

 shoot completely dead, and its trunk had scarcely increased 

 in girth at all. I do not see what else will account for this 

 difi'erence, except a difference in individual constitution, 

 rendering the latter more sensitive than the former to the 

 influence of the intensely cold weather of December 

 1879. 



Experience having given me confidence in the minute 



