172 
THE FLORIST AND POMOLOGIST. 
[ August, 
ing of fruit. From repeated experiments and observations, extending over 
twelve years, I believe that an atmosphere containing from 75 to 80 per 
cent, of vapour by day, and allowed to become saturated at night, will not 
only cause Vines to generate, but also to develope aerial roots in abun¬ 
dance ; while on the other hand, if the vapour be daily reduced to from 55 
to 70 per cent., none will make their appearance, not even if the air is 
allowed to become nightly saturated as in the former case ; nor will any 
evils result to the foliage from this state of dryness, provided the roots are 
in a healthy, active state. 
I am well aware that these opinions are in some respects opposed to the theory set forth 
by our great teacher Dr. Lindley, who stated that “ The formation of aerial roots is an un- 
mistakeahle sign of the coldness of the border ,” and in the experiment which he mentions 
with the Vine in a nearly air-tight frame, he attributes their presence to the same cause; 
hut I would ask, Would not the excessive vapour which must necessarily exist in a nearly 
air-tight frame, he quite as likely to produce them? The Verbena and Pelargonium in our 
flower gardens will occasionally form air roots in calm, moist, mild autumns. Neither cold ¬ 
ness nor dryness at the root can he the cause, for the air and earth temperatures nearly coin¬ 
cide at that season of the year. The question, Why are some sorts of Vines more subject to 
this peculiarity than others? is as easily answered as the one, Why do some require a 
higher temperature than others ? One possesses a hardier constitution, and requires less heat; 
another is suited to a drier climate, and requires less moisture. The Muscat of Alexandria 
will thrive well in an atmosphere sufficiently moist to cause the Gros Golman to curl like 
parched paper when the sun shines upon them. 
Wilton House Gardens. Thomas Challis. 
’HERE are many tilings in nature which may be described as to their 
progressive development, while yet their primary cause remains be¬ 
yond all human ken. A seed of grass may and will germinate under 
and upon soil, on polished marble, on a sheep’s back, or in a spider’s 
web. Its position is varied, but the moving power is the same ; and 
according to its special peculiarity of position, there must be modifications 
in the elements of that power to attain like results. Under the influence 
of light, heat,and moisture, the seed germinates; so in the case of aerial 
Vine roots, “ ’tis their nature to ” produce them. Their projection may be 
accelerated by “ unripened wood,” but it is a fact that they are very often 
projected abundantly from well-ripened wood; it may be accelerated by “want 
of reciprocity between root and branch and yet it is a fact that they are 
in other cases minus under the same circumstances, and that they are 
abundantly produced under a genial spontaniety of action in root and branches. 
But there is not a doubt that shade with a “ warm humid atmosphere,” in a 
stagnant state, and with a weak constitution, is the principal agent in their 
production. They are as natural to the Vine as any other part of its 
structure; its system is permeated by their presence, either in, an active 
or more or less latent state. Whatever tends to the debility of the Vine’s 
constitution adds increased power to their vitality; and under artificial 
and foreign culture this is easily aggravated. The mechanical and chemical 
