SCIENTIFIC SUMMARY. 
507 
appeared upon this subject. The number of useful plants has been com- 
puted to be 12,000, but it must be remembered that the researches which 
lead to this conclusion hace only extended over certain parts of the world. 
There are no less than 2,500 known economic plants, among which are 
reckoned 1,100 edible fruits, berries, and seeds ; 50 cereals ; 40 uncultivateel 
edible graminaceous seeds ; 23 of other families ; 260 comestible rhizomes, 
roots, and tubers ; 37 onions ; 420. vegetables and salads ; 40 palms ; 32 
varieties of arrow-root ; 31 sugars, and 40 saleps. Vinous drinks are obtained 
from 200 plants, and aromatics from 266. There are 50 substitutes for 
coffee and 129 for tea. Tannin is present in 14 plants ; caoutchouc in 96 ; 
gutta-percha in 7 ; resin and balsamic gums in 389 ; wax in 10 ; grease and 
essential oils in 330 ; 88 plants contain potash, soda, and iodine ; 650 contain 
dyes ; 47, soap ; 250, fibres which serve for weaving ; 44 for paper making ; 
48 give materials for roofing ; 100 are employed for hurdles and copses ; 
740 are used in building, and 615 are known to be poisonous. According to 
Endlicher, out of 278 known natural families, there appear to be only 18 
absolutely useless. — Vide Cosmos I. 283. 
A Neiv Species of Docidium from Hong-Kong is described by Mr. W. Archer 
in The Dublin Quarterly Journal of Science, No. XVIII. The frond is 
about five times longer than broad, and is stout ; the suture forms a some- 
what prominent ring. The segments are about two and a half times longer 
than broad, slightly and gradually tapering, with four prominent transverse 
whorls of short stout hyaline quadri-partite spines, their points divergent 
and sub-acute, and with a fifth whorl just under the ends, of short, stout, 
sub-acute, simple spines ; ends broad and truncate. The terminal space in 
the endochrome is large, circular, and well-defined, and the active granules are 
very numerous. Mr. Archer has given it the specific name Kayei, in honour 
of the gentleman who first observed and sketched the specimen. 
Is Desmarestia Pinnatinervia a Distinct Species ? — Dr. J. E. Gray, who by 
no means gives up his attention exclusively to the study of animals, has a 
paper on the relations of this alga in the J ournal of Botany for June. The 
specimen, which was forwarded from the coast of Cornwall, had been found 
growing from the root of a specimen of D. ligidata, near the Lizard. There is 
good reason for the supposition that D. pinnatinervia is but a broad form of 
the Europe^in D. ligulata. The Cornish specimen. Dr. Gray thinks, goes far 
to justify the theory ; for the specimens were found growing from the same 
root as the typical English form of D. ligidata, and if the frond is compared 
with the thin young state of that plant, and especially with the broad 
membranaceous variety of it found in Cornwall and on the west coast 
of France and Spain, there is no structural difference to separate them 
— the only real difference being that the frond is much wider and, for 
its size, comparatively thinner and more membranaceous. Dr. Gray is 
not inclined to regard it as a variety of D. ligulata, but as a particular 
development of some of the fronds of that species, for he has been infomed 
that it absolutely grows from the same root-disk, and that many of the roots 
have one or more such fronds developed along with the usual narrow state 
of that plant. 
Our Colonial Cinchona Plantations. — Sh: William Hooker, in his annual 
report of the progress of the Eoyal Gardens of Kew, states that inost 
