forward no pretension to dogmatize, or to know better than others. In striking contrast to such an honourable diffidence, we have seen some Continental writers,-and those not mere sciolists, but men of unquestioned ability,-criticize with a strangely misplaced ridicule, and an unwarranted affectation of superior knowledge, the speculations of so earnest a truth-seeker as Mr. Darwin,-an author whose scrupulous attention to objections and difficulties is so remarkable, that he certainly often suggested such as would not have occurred spontaneously to his opponents. His abstinence from dogmatism on questions which had so long engaged his attention, whilst one of the most pleasing, is at the same time one of the most honourable characteristics of Sir W. Hooker's writings; and there can be no surer test of an honest devotion to science, as distinguished from a desire of self-aggrandisement through its study, than such a becoming admission of humility, in the face of the great and solemn problems of nature.

British Vice-Consulate, Whampoa,

18th March, 1866.

THE INTRODUCTION OF LEPIDIUM DRABA INTO

BRITAIN.

The introduction of a new plant that takes its rank amongst our own indigenous ones should be carefully noted, or in a few years the generation will have passed away, and sometimes all record of the plant with it. Many of our so-called British plants had doubtless a European origin, and even some came originally from parts of the earth yet more distant. There are many persons yet living, who remember the disastrous Walcheren Expedition; but few are aware that to the effect of this is to be ascribed the introduction of Lepidium Draba, the most troublesome weed to agriculturists, saving Gravel Bine, Convolvulus arvensis, for, like it, the new-comer dives deeply into the earth, from 8 to 9 feet, and cut it or break it off as you will, new buds are formed and shoots developed that in time will find their way to the surface, luxuriate in leaves and flowers, from which, in due time, seeds are produced and the race extended. All this increase by seed the husbandmañ can prevent by cutting off the tops; but how is he to rid the soil of the roots thus deeply seated ? Again, when the

deeply seated bud has forced up a spindling weakly-looking shoot to the air, the very first effort (in which it is usually successful) is to thrust out lateral thready roots in all directions within from 6 to 12 inches of the surface, and often extending to 6 feet and more. These ramifications are full of buds, and the second year produce a plentiful supply of herbage and flowers, as just recorded. But it is time that I explain its denizenship, and its connection with the Walcheren Expedition. When our troops returned to England many disembarked at Ramsgate; the poor fellows were suffering under malarious fever, and their beds were ripped up and the straw, etc., was placed in an old chalk-pit belonging to a Mr. Thompson. Time passed on, and this heap of refuse was mixed with seaweed and manure, and finally employed to fertilize the fields. Wherever this was done a plentiful crop of the new weed was produced, and which to distinguish it was called Thompson's weed. We have traced its introduction, and its spread over many parts of the Isle of Thanet; it now remains to show its future progress. It seems to take to the edges of ditches, the edges of footpaths, etc., in preference to the open fields, and may be traced through Canterbury, Chatham, and to Sittingbourne, Gravesend, Deptford, Peckham, etc., as I have done; but how far it has reached towards the northern and midland counties I have had no opportunity of ascertaining. It may be well, however, for me to state, that I have measured one root in the chalk where it was originally brought, that was 9 feet long, and then did not reach the extremity. (W. M. in 'Gardeners' Chronicle.')

ON A NEW SPECIES OF TACCA.

BY THOS. NUTTALL, ESQ.

[When lately working up the different species of Tacca for my Viti Flora, I was unable to procure a sight of the American Journal of Pharmacy' (of which there does not exist a copy at the British Museum, nor a complete set at the Pharmaceutical Society of London, nor, as far as I know, anywhere else in Europe), and I could therefore not clear up the synonymy satisfactorily, owing to T. oceanica being described in the ninth volume of that useful periodical. Pro

fessor Asa Gray has been good enough to obtain for me a transcript of the description and tracing of the figure of T. oceanica, known to me only from a reference in Pereira's Materia Medica.' As others may find themselves in the same difficulty as I was, it may be desirable to reprint the description. I may add that T. oceanica proves identical with Forster's T. pinnatifida, and that the Indian plant hitherto included under that name will probably have to receive a new name.— B. SEEMANN.]

1

Tacca oceanica, maxima, foliis palmato-quinquepartitis coadunatis, laciniis acuminatis, ultimatis trifidis; involucrum foliolis lato-ovatis sublobatis breviusculis.

Habitat.—In rich shady woods, towards the mountains in Tahiti, and probably other of the Friendly Islands, as well as in Wahoo, Owyhee, and Atovi, of the Sandwich group.

Description. The root consists of numerous yellowish-white-skinned tubers, scattered over with eye-buds like so many potatoes, and are, in fact, scarcely distinguishable from the roots of that common vegetable ; from these arise in the summer season, clusters of tall spreading palmately-divided smooth leaves, from two to three feet high, of which length the foot-stalk forms two-thirds or more; the leaf itself extends out to the breadth of eighteen inches or two feet, and is divided into three primary divisions, and two others which are lateral, or come out above the base of the side divisions; these principal divisions are divided very much in the manner of our red oak leaves, or pinnatifid towards the base, and more or less dilated and three-lobed beyond; each of the principal divisions again inclining to be three-lobed, except the central one, which is usually pinnatifid as well as terminally three-lobed; all the divisions end in acuminated points, and are, below, everywhere confluent into each other, down to the primary divisions or summit of the footstalk.

The leaves are probably possessed of some degree of succulence, but the vessels beneath present a strong, almost pinnated outline. The scape or flower-stem, in the only specimen I possess, is very stout, and rather more than three feet high, attenuated towards the umbel, whose involucrum consists of about two series of broad, ovate, acute, and sometimes slightly three-lobed leaves, which appear to have been white, or some brighter colour.

The umbel consists of numerous longish, pedunculated, small, brown

or brownish-red flowers, nearly campanulate, and consisting of a calyx only within there are six hooded, petaloid, pedicellated bodies, answering both the purposes of petal and filament, each containing and almost concealing (as in the infertile anthers of the Larkspur) the 2-celled anthers.

With the berry and germ I am unacquainted. As in the T. pinnatifida, there are interspersed among the flowers numerous abortive filiform peduncles, which form a crinite tuft extending far beyond the flowers. The root of this plant, or the tubers, when pounded and washed, afford a fecula, which, under the name of Pia, is used extensively in the Sandwich Islands as an article of food, and goes among the white residents usually by the name of Arrow-root.

The present species is readily distinguished from that of India, by the broader, more divided, and coadunate leaves, as well as by the short and broad leaves of the involucrum; it is also, apparently, a larger plant in all its parts, save the flowers.

A NEW BRITISH STATION OF WOLFFIA ARRHIZA. Mr. M. Moggridge has been fortunate enough to discover a new station of Lemna, or rather Wolffia arrhiza. He found it on July 7, in a pool in the second field south-east of St. James's Church, Walthamstow, Essex. The plant being smaller than a pin's head, and occurring in company of other Duckweeds, has probably been overlooked in many localities, and it is highly desirable that our correspondents should carefully examine their respective neighbourhoods with a view of finding this new British plant. We shall be glad to insert any communications on the subject that may be forwarded, so that the geographical range of this species may be worked out. That it is not a recent importation to our islands appears from the subjoined letter. British Museum, July 28, 1866.

About fifty years ago Mr. Bennett and myself had some specimens of Lemna arrhiza, brought to us as having been discovered in the neighbourhood of London, I believe Putney Common. It was collected by M. Gérard, an old Frenchman, who had been head gardener at Versailles, but had emigrated at the first revolution. He was a good botanist, and supported himself by collecting plants and selling