GROWTH OF PLANTS IN CLOSED GLASS VESSELS. 503 
_ situation. I then, through the kindness and liberality of Messrs. 
Loddiges, who well deserve the title of ‘Hortulanorum principes,’ 
commenced a series of experiments upon plants of all structures, 
and belonging to a great variety of natural families, which has 
continued uninterruptedly to the present time. 
__ Before I proceed to state the results of these experiments, it 
__ may be as well to say a word or two respecting the cases in which 
they were carried on. These cases are of all sizes and shapes, 
from sinall wide-mouthed bottles to a range of houses about 25 
_ feet in length and 10 feet in height. These houses are filled 
_ with rock work for the purpose of accommodating the various 
_ descriptions of plants I had to deal with. Some of these cases 
are quite closed at the bottom, and when once watered, require 
no further watering for a long period, while others have several 
Openings, and the plants are watered occasionally, once in three 
or four weeks, or months, as they may require. I believe that 
this latter plan is the best, as there is then no danger from ex- 
cess of wet, and should worms or slugs make their appearance, 
they can readily be destroyed by the free use of lime water. The 
_ glazed roofs and sides of these cases are made as tight as putty 
_ and paint can effect, and the doors fit closely. In no instance 
B. have I ever endeavoured to seal the cases hermetically ; it would, 
_ I conceive, be almost impossible to do it, and if done, would 
_ prevent that continued changeof air, from its alternate expansion 
_ and contraction, upon which in my opinion the success of the 
_ plan mainly depends. I have already explained myself fully 
_ upon this point in my letter to Sir W. Hooker, and should not 
_ have thought it necessary to have alluded to it again had I not 
seen that Professor Henslow, in his Descriptive and Physiolo- 
_ gical Botany, a work of the highest authority, entertains this 
mistaken notion. With respect to the management of the plants 
in the cases, I have always endeavoured to imitate their natural 
_ conditions as nearly as possible, being fully sensible of the value 
_ and truth of that remark, “ that we can command Nature only 
_ by obeying her laws.’ It would be impossible in the necessarily 
_ short limits of this report to enter into any lengthened details, 
and I shall therefore give as concisely as possible the results. 
1. That the change of air produced by alternate expansion 
and contraction is regulated by the heat, and is therefore exactly 
_ proportioned to the increased wants of the plants arising from 
their greater excitement. Vascular require a greater change of 
_air than cellular plants, and this is effected by surrounding them 
_ with a larger volume. 
2. It is of great importance that light be freely admitted to 
_ all parts of the growing plant, assisting it in the development 
2L2 . 
