100 AIROPSIS. 
improves the tone of the stomach, strengthens the 
lungs, and promotes the general health. 
AIROPSIS. A small genus of exotic grasses 
of the Agrostis family, but taking the name of 
Airopsis from its close resemblance to the genus 
Aira of the Bromus family. Seven species are 
known; two of these, the short-leaved and the 
agrostis-like, have been transferred from the 
genus Aira; and three, the handsome, the glo- 
| bose, and the obtuse-leaved, have been introduced 
to Great Britain within the last twenty years. 
All are perennial and hardy ; but they are either 
quite uninteresting to the farmer, or at best but 
curious. 
AIR-PLANTS. Plants which can live sus- 
pended in the air, independent of soil, and draw- 
_ ing all their nourishment from the gases and the 
| moisture of the atmosphere. 
They require, of 
course, to be supported by some suspending ob- 
ject, but they derive from it only a mechanical 
_ use, and do not, like lichens and fungi, treat it as 
_ a source of nourishment; and though they have 
the power of living by suspension, they sooner 
lose their energy, or exist during a considerably 
shorter time, than if they were supported and 
partly nourished by the soil. All are natives of 
very hot countries, and belong to the two tribes 
Bromeliacee and Orchidee. The moss-like 7%- 
landsia usneoides grows in festoons upon the 
branches of trees in the moist districts of tropical 
America, and the sweet-smelling 7%llandsia xiph- 
zoides adorns the balconies of houses in Buenos 
_ Ayres; but these—which are the chief Bromelia- 
ceous air-plants—have hitherto not been culti- 
| vated in this country. Even Orchideous air- 
| plants—though they comprise many hundreds of 
beautiful species, and though they have of late 
years become somewhat common in the _hot- 
houses of good florists—were, at a recent period, 
regarded in Europe as distant and almost fabu- 
lous wonders of the Hast, and even yet are far 
from being properly understood by many garden- 
ers and amateurs who have attempted their cul- 
tivation. The most conspicuous genera are Aer- 
ides, comprising about eleven species, Vanda, 
comprising about six species, and Sarcanthus, 
comprising about five species; and the first of 
these, as their name implies, are the type of the 
whole air-plant tribe. ‘The true species of this 
genus,’ remarks Mr. Loudon in his Encyclopedia 
of Plants, “are beyond all comparison the most 
delightful productions of the vegetable world. 
Their flowers are arrayed in long spikes or ra- 
cemes of delicate colours and delicious fragrance. 
Hung up in a room in their native country, a 
little before flowering, they continue to unfold 
their blossoms in gradual succession for many 
weeks.” The air-plants naturally abound in the 
damp, hot, shady forests of the torrid zone of 
both the old world and America, hanging on the 
branches of trees, clinging to rocks, or creeping 
among moss, by the side of fountains or close to 
AJUAPAR. 
Brazil, Peru, Mexico, the West Indies, Madagas- 
car, Nepaul, and the whole of the Indian archi- 
pelago; they have’been found, to the amount of 
three hundred species, in the single island of 
Java, and are described as there overmatting the 
trees by thousands, and combining with huge 
climbers and gigantic grasses to maintain among 
the forests a perpetual dampness and gloom; and 
when artificially cultivated in the hot-houses 
of Britain, they require a high temperature, a 
shaded or gloomy light, an exceedingly moist 
atmosphere, a dry position for their roots, and, 
above all, an annual season of repose. The 
neglect of the last of these requisites, far more 
than the neglect of any of the others, has hitherto 
occasioned them to languish or die with numer- 
ous cultivators. But ifa fair proportion of gar- 
deners will keep them growing during two-thirds 
or three-fourths of the year by means of heat, 
shade, moisture, and perfect drainage—and will 
throw them into repose during the remainder of 
the year, by withdrawing from them nearly all the 
moisture and most of the shade—air-plants of 
surpassing beauty and exquisite fragrance may 
soon become the gorgeous and delicious orna- 
ments of our dwellings,—suspended from the 
ceilings, and diffusing clouds of odours, as they | 
have long done in the houses of the CRIEESe. me 
AERATION and ORCHIDER. 
AIR-VESSELS. Vegetable vascular organs, 
supposed by some vegetable physiologists to be 
employed in the inhalation of air. The spiral 
tubes of plants are regarded by most physiologists 
as vessels for conveying sap; but they were sup- 
posed by Drew and Decandolle to possess some 
slight resemblance in structure to the trachez of 
animals, and presumed to be used like these 
organs for the conveying of air. But air seems 
to have free access to the leaves and to other 
parts of plants quite independently of the spiral 
tubes; and strong reasons exist for concluding 
that Drew’s and Decandolle’s opinion of these 
vessels is unsound. See article Vascutar Or- 
GANS. 
AJUAPAR—botanically Hura. Asmall genus 
of tender, evergreen shrubs or small trees of the 
euphorbia family. Only two species, Crepitans 
and Strepens, are known; and both are natives 
of South America and the West Indies. The 
Ajuapar is remarkable for its milky-looking juice 
of poisonous quality. It was found in the Span- 
ish West Indies, and introduced thence to the 
British American colonies; and about eighty or 
ninety years ago, it became pretty common in the 
superior class of English gardens. It was ori- 
ginally called by Hernandez Arbor crepitans ; and 
it afterwards received the popular names of the 
sand-box-tree, and the Jamaica walnut-tree. It 
acquires a height of twenty-four feet in the West. 
Indies, but of only twelve or fourteen in England. 
Its stem is ligneous but soft; its branches are 
numerous, scarred, and very juicy ; its leaves are 
| the spray of waterfalls; they occur principally in , heart-shaped,—the largest eleven inches long and 
