28 ACCLIMATATION. 
often throws out blossoms of the two parent species, along 
with the hybrid, so that the three sorts are found all in flower 
on the tree at the same time. 
About twenty years ago I planted on the margin of a 
stream that runs past my house a plant of the purple laburnum. 
It occupies a cool soil, only about three feet above the rise of 
water ; for the first ten years it grew luxuriantly, and gene- 
rally flowered very well, but it did not ripen its wood well, and 
being tender, it required to be frequently divested of dead 
wood, particularly after a severe winter. After being about ten 
years planted, it broke out here and there through the tree 
with tufts of the purple dwarf cytisus; these tufts or bushes gene- 
rally died down to the branches from which they emerged, and 
were pruned off along with the other dead wood throughout the 
tree. After this process of discharging, or throwing off the ten- 
der element for a few years, twigs began to appear of the com- 
mon laburnum, which yielded blossoms of unusual size ; the 
racemes produced seed which grew very vigorous plants of the 
common laburnum, although the three sorts continued for a 
few years very visible on the same tree, all from the one 
scion or graft of purple laburnum, yet the cold summers 
succeeding 1860 caused the hardy common tree variety to 
shoot ahead, and it has now completely extinguished the 
tender grafted kind, and ripens its shoots in the coldest 
season, and continues to grow vigorously. What renders this 
tree so interesting is the facility with which it adapts itself 
to the character of the seasons. It was only in the warm 
months of 1865 that the tufts of the cytisus purpureus again 
became perceptible, the tree having during the previous four 
or five cold seasons almost wholly returned to the hardy com- 
mon Alpine or Scotch laburnum. 
There is no tribe of plants with which I am acquainted that 
is so susceptible of climatic influence as the Conifer. In the 
celebrated native pine forests in the highlands of Morayshire 
any variety among the trees can hardly be distinguished. But 
I have taken seeds from these, and after raising them, have 
planted them on the warm sands only a little above the level 
