221 
over them, placing the under side of such leaves at all times 
undermost; by which means a humid atmosphere is preserved, 
whilst the powerful sun is upon them. The last two years I 
have used no shading, as I have had no time to attend to it, 
and few plants have missed. The pipings are best left with 
no other attention after planting, besides occasional watering, 
in dry weather, and keeping them free from weeds till time for 
planting out, which may be done at any time after the plants 
are perfectly rooted : the usual season, however, to plant out 
for flowering in the highest perfection is September; and for 
propagation, all the month of June, even to the middle of 
July. 
237 Propagation of Trees by Cuttings. The following 
experiments, made by the late Thomas Andrew Knight, are 
I'ounded on a principle, Avhich, if properly regulated, may 
greatly facilitate the propagation of such ligneous plants, as 
have hitherto proved difficult of increase. Many practical 
cultivators have thought that some cuttings emit roots more 
freely if not deprived of any of their leaves, still as the results 
of their experience have not been elucidated by physiological 
eiupiiry, they have hitherto gained but little attention. Many 
of our readers will have pleasure in following the close reason- 
ing of Mr. Knight’s philosophic mind through the following 
article, which was read before the London Horticultural 
Society in 1838; and we hope that some of them will carry 
out and perfect the practice to which it points with so fair a 
promise of success. 
“ When a cutting of any deciduous tree is planted in autumn, 
or winter, or spring, it contains within it a portion of the true, 
as it has been called, or vital sap, of the tree of which it once 
formed a part. This fluid, relatively to plants, is very closely 
analogous to the arterial blood of animals ; and I shall there- 
fore, to distinguish it from the watery fluid, which rises 
abundantly through the alburnum, call it tlie arterial sap of 
the tree. Cuttings of some species of trees very freely emit 
roots and leaves : whilst others usually produce a few leaves 
only and then die ; and others scarcely exhibit any signs of 
life ; but no cutting ever possesses the power of regenerating, 
and adding to itself vitally, a single particle of matter, till it 
has acquired mature and efficient foliage. A part of the arterial 
211. AUCTABIOM. 
