408 NOTICES OF THE MEETINGS [March 17, 
covering is fitted on, and the case placed in a situation where it 
may be exposed to a due amount of light, but for ferns, not to 
the full force of the sun’s rays. For the drainage of superfluous 
water, it is necessary either to have apertures perforated in the 
bottom of the case, or, what is better, a depression in a corner from 
which such water may be removed by means of a sponge or syringe. 
In a case so arranged, the several natural conditions of plants are 
fully realized. The closely-fitting glass covering, while it excludes 
soot and dust, admits freely the light which is essential to the 
vigorous and healthful growth of plants, since without it they are 
not duly nourished, and grow devoid of odour and colour, sickly and 
unattractive in aspect. In the next place, the water with which the 
mould has been saturated, and without which neither seeds nor 
plants can develop or grow, is retained or escapes only in inap- 
preciable quantities. Exhaling from the leaves and rising from 
the mould in the form of vapour, it becomes condensed on the 
surface of the glass in the form of small beaded drops which, 
coalescing, form streamlets that course down the side of the 
glass: the water is again absorbed by the mould, evaporated and 
condensed, and so keeps up a ceaseless circulation. The plants 
in a bottle which was exhibited had had no fresh water for nine- 
teen years. Again, the perfect tranquillity of the air within the 
case enables the plants to bear both higher and lower degrees of 
temperature than they would do if exposed, because the protective 
vapour which surrounds them is not carried off. For this reason, 
a glass shade placed over cut flowers preserves them in a state 
of freshness for a considerable period. And, lastly, with regard 
to the admission of air. The case is not, and cannot be her- 
metically sealed or air tight. If it were, the first change in the 
relative temperature of the air within and without would result 
in the fracture of the glass. Change of air is effected very 
subtly, but must ever be going on in obedience to the diffusion 
law by which gases of different density become intimately blended ; 
rising against the attraction of gravitation, passing through bladder 
and other membranes, and through barriers more complete than 
a glazed frame-work which is only nicely adapted to, not amal- 
gamated with the case below. 
While the different natural conditions are realized in one of 
these cases, they may be so modified as to suit the requirements 
of different kinds of plants. Ferns generally require a peaty mould, 
a humid atmosphere, and a moderate supply of light. Asan instance 
of the perfection to which they will attain under this plan, may 
be noticed the success which has attended one of the most deli- 
cate, the Trichomanes speciosum. In the first experiment made 
with this, the fronds attained a size one fourth larger than native 
specimens either from Killarney or Teneriffe; and Mr. Callwell of 
Dublin has a plant which, remarkably slow as this fern is of 
growth, has produced in nine years three hundred fronds varying 
