April 28, 1881. ] JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
regions, as Taxodium, Thujopsis, Chestnuts, Oaks, Walnuts, a Mag¬ 
nolia, and a Plum had been found fossil in Greenland, Maple and 
lulip Tree in Iceland, and forests r of deciduous trees seem to have 
flourished where land is now perpetually icebound. 
ith regard to the origin of this similarity Dr. Unger considers the 
emigration to have taken place from America to Europe. He thinks 
the living flora of the eastern States of North America is the lineal 
descendant of that which gave rise by aid of “ Atlantis,” a supposed 
submerged land, which is thought to have connected Europe with 
America, to the Swiss Miocene flora. Sir C. Lyell thought the route 
taken was the longer one round by Japan and not by Atlantis ; but 
still from America to Europe. Instead, however, of regarding either 
Switzerland or the South United States as the origin, there remains 
the theory of Professor A. Gray, that as the Miocene flora appears to 
have been uniformly spread over the whole of the regions bordering 
the Arctic circle, so, when the northern climates became cooler in 
the next or Pliocene age, this flora was driven southward along every 
meridian, its descendants now' existing in the localities above men¬ 
tioned. These now form a belt, roughly speaking, between the 30th 
and 40th parallels of latitude. Migration to some extent might have 
taken place along that belt, but the greatest migration was probably 
from north to south. 
The lecturer next called attention to the collection of Clematis ex¬ 
hibited by Messrs. Yeitch, pointing out its connection -with the Butter¬ 
cups by means of Anemone. He alluded to the calyx being coloured 
and so superseding the necessity of a corolla, though this was pre¬ 
sent in the sub-genus Atragene. He described the European forms 
introduced in the sixteenth century and the splendid Japanese 
kinds imported within the last fifty years which have supplied the 
innumerable existing handsome sorts. The method of climbing by 
means of the petioles or leaf-stalks, which are sensitive to touch, 
formed the subject of some remarks. A fine specimen of Cineraria 
from Mr. Cannell’s, which was named “ Marched Past ” was shown 
as well as a branch from the old original C. cruenta, for comparison, 
which well showed what the florist’s skill had accomplished. 
DENDROBIUMS. 
Orchids are now represented in the gardens of this country by 
considerably over a thousand species and distinct varieties, of 
Fig. 77 .—Dendrobium crassixode. 
which probably nearly a fourth are included in the genera Den- 
drobium, Odontoglossum, and Oncidium. In the number of 
species cultivated these genera are nearly equal, and with the 
exception of about three species all have been introduced within 
the present century, thus affording some idea of the attention that 
has been paid to this most interesting and beautiful family of plants. 
Sweet’s “ Hortus Britannicus,” published in 1826, enumerates but 
twelve species of Oncidium, only three of which were grown 
in the last decade of the eighteenth century ; ten species of 
Dendrobium are named, all introductions of the present century ; 
while the genus Odontoglossum is quite unrepresented as one of 
the earliest grown, O. bictonense did not appear until ten years 
after the date of Sweet’s work. Now there is not less than a 
hundred species of each genus in cultivation ; and with the varie¬ 
ties, some of which are almost distinct enough to deserve higher 
rank, a total closely approaching four hundred is obtained—a 
remarkable increase in fifty years ; but these numbers only refer 
to the forms grown in English gardens, and probably there are 
twice as many known to botanists. 
Leaving for the present the Oncids and Odontoglots, a brief 
review of the leading characters and most beautiful forms of the 
Dendrobes will enable some idea to be formed of the extent and 
diversity of this handsome genus as it is known at present. In 
few other groups of Orchids is so great a range of variation in 
habit noticeable as among the Dendrobes. Some have erect or 
pendent cylindrical jointed stems several feet in length ; others 
have large club-shaped pseudobulbs, and a few have diminutive 
pseudobulbs an inch or two in height. In the modes the flowers 
are borne there is nearly the same diversity ; some are produced 
singly in pairs or in triplets from the nodes of the stems, others 
are borne in dense racemes, and still others in long lax racemes. 
The flowers, too, vary greatly in size, and many beautiful shades 
of colour are represented ; purples and yellosvs are particularly 
abundant, the rich golden tints in some of the species- being unex¬ 
celled in the whole order. The species are epiphytal, and chiefly 
inhabit the East Indian continent or the numerous islands in that 
region, but very widely separated portions of the earth’s surface 
also contribute representatives of the genus. For instance, 
