P. imperialis. - This magnificent tree was spoken of in the first edition as being perfectly hardy. It had proved so at that time (1851), having stood well for two winters, but it had not shown any indication of bloom; since then, the clusters of flower-buds, which show themselves in autumn, have been produced repeatedly, but in every instance have perished the following winter. In the winter of 1854-5, which was a severe, open one, the tree was partially killed, but revived in the summer following, and grew very luxuriantly. The tree was in an exposed situation. Perhaps, in a more sheltered place, it would have met a different fate; but it is a tree liable to be destroyed or greatly damaged in almost any location in the northern part of New England. In New Jersey it has bloomed finely; but in Washington, D. C, this winter (1855-6), I understand the flower-buds have been all killed by the severe cold.