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There are, however, in all this area certain indications of the proximity of old land and of pre-cretaceous denudation, in the presence of Quartz and Lydian-stone pebbles, accompanied by extraneous secondary fossils in the Lower Greensands of Surrey, and in the like old-rock pebbles, with the addition of slatepebbles, in that formation in north Wiltshire; while the banks of shingle, bryozoa, and sponges of the same age at Faringdon, point to still and sheltered waters, probably of no great depth, and to adjacent dry land. Again, on the north of London, we have in the Lower Greensand of Buckinghamshire and Bedfordshire shingle-beds consisting almost entirely of fossils derived from Jurassic strata, with a remarkable collection of larger quartz, quartzite, and other rock pebbles, probably from the old palæozoic axis, which at first stood out in the midst of the Lower Secondary seas, and was only finally submerged in the seas of the Gault and Chalk periods. It was no doubt owing to the gradual shallowing of the old seas as they approached the then palæozoic land that the thinning out of the Lower Secondary rocks from the north-west to the south-east, which we before noticed, is owing.

In this country the newer strata, overlying the paleozoic rocks on parts of the presumed old palæozoic range, have been sunk into without result-in the Wealden at Hastings to a depth of 486 feet, in the upper beds of the same at Earlswood, near Reigate, to about 900 feet, through chalk at Chichester, to 945 feet, and at Southampton, through Tertiary strata and chalk, to a depth of 1,317 feet. Unfortunately all these works fall short of the mark which we as geologists wish to attain.

In a scientific point of view, no experiments could have greater interest, and in an industrial point of view no experiments could be more important, than such as would serve to determine the position of this great underground range of older rocks connecting the Ardennes and the Mendips. We have ascertained that it lies at no great depth beneath the overlying newer strata, and if the strike of the line of disturbance were in a straight line, we should have no difficulty in determining its course; but from what we know of its range in the proved part of the 800 miles, it is certain that while it has a general east and west bearing, it is subject to considerable local deflections. Thus, while Mr. Godwin-Austen is disposed to place the supposed coal trough in the Valley of the Thames or under the North Downs, I am disposed to place it further north, in Essex and Hertfordshire; and while my friend considers it continuous, I consider it to be most likely broken up into basins. Again, if the axis of the Ardennes consisted of an anticlinal line, the problem would be simplified, but it consists of a series of such parallel lines, and therefore whether or not the one which

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traverses the Boulonnais and is probably prolonged under our Wealden area, is one of the many central ones, or the lateral one immediately flanking the coal trough, is uncertain.

Any attempt made to solve this great problem must be hailed with satisfaction, and we therefore look upon the trial about to be made by the Sub-Wealden Exploration Committee as a most important step in this direction. The site selected for the experiment near Battle is on the line of centre of the Weald, where the lowest Wealden beds come to the surface, and it is no doubt on or near the line of continuation of the axis of the Boulonnais. We may, therefore, there expect to meet with a prolongation of that axis consisting either of the Mountain Limestone, with the subordinate coal strata of Hardinghen, or the Devonian Limestone and grits. Had it been merely a trial for coal another site might have been selected, but the object the Committee has in view is one purely scientific, to determine the thickness of the Wealden and underlying secondary strata, and the depth, nature and position of the underlying palæozoic rocks; and it has been suggested and planned in honour of the next meeting of the British Association at Brighton —of which meeting it will be a worthy memorial. It is not by one experiment, however, but rather by several, that the important question of the line of the great trough of productive Coal Measures will be determined. This experiment will probably be but one of a series. We hope to learn by it the direction of the strike of the older palæozoic rocks, and then judge of the bearing and probably position of the coal trough in relation thereto. No insurmountable difficulties present themselves. The starting-point is the lowest in the series of the known rocks of the south-east of England, and if it should prove to be on the crest of the prolonged ridge of the Boulonnais, the other secondary strata may be of no great thickness. But this is entirely a matter of experiment. We know not what may be the thickness of the remainder of the Wealden, and if beneath that we find the Purbeck and Portland beds, the Kimmeridge clay, and some of the Oolitic series in place, as we do in the Boulonnais, we know not what thickness they may attain.*

The thickness of the strata may vary within the following limits:

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The Committee wisely contemplate the possibility of having to go to a depth of 1,500 to 2,000 feet, and will, we trust, take secure steps against such a contingency. At the same time we hope (and it is perfectly possible) that before they reach half that depth, the very interesting object of which they are in search. may meet its solution, and that one more positive fact may be acquired to science in addition to those so fortunately furnished by the trial works at Kentish Town and Harwich.

244

BUD VARIATION.

BY MAXWELL T. MASTERS, M.D., F.R.S.

THE reproduction of plants is effected in one of two ways,

either by the contact of one elementary organism with another of a different kind, in consequence of which a spore or an embryo is formed, which ultimately developes into a perfect plant, or by the production of buds.

The word bud is here used in a broad sense to express any separable portion of a plant, not produced by sexual agency, and which when separated has the power of growing into an organism like the parent plant. The process of bud-formation then, reduced to its simplest expression, is a process of segmentation, or subdivision. Illustrations are to be found throughout the whole vegetable kingdom, but in no family are they more frequent, or do they play a more important part, than in the great group of the Fungi, among which are the moulds and blights so destructive to the higher plants on which they grow. One of the most remarkable circumstances about these plants is the varied manner in which they are reproduced. Spores, or reproductive bodies of four, five, or more shapes are met with at different times on the same plant, and, inasmuch as they are often formed at various times and under diverse conditions, it is no matter for surprise that they should have been assigned, not to the same plant, but to different ones, and hence each one has had the misfortune of being separately named.* Now, thanks to the labours of those who have, with infinite skill and patience, succeeded in unravelling the life-history of these plants, all these varied forms are known to be different states of the same plant. Of these spores some are true reproductive bodies in the sense already explained, while others are buds extending and multiplying the plant, but not reproducing it. We do not know in all cases, indeed we only know in a few,

See a paper on the subject of Polymorphism in Fungi, in "Popular Science Review," Jan. 1871, y Mr. M. C. Cooke.

the complete life history of these plants and the particular office the bud-like formations fulfil. For our present purpose, however, it will suffice to say that they vary in size, form, and apparently in the conditions under which they are produced. In spite of these diversities, we know that they develop into organisms precisely like those from which they sprung.

Among the sea-weeds the same state of affairs exists; there are true spores and bud-spores, and these bud-spores vary in character on the same plant at different times and in different

seasons.

In the Lichens we have a similar formation of true spores and bud-spores, but so far as is at present known, there is not the same diversity in the bud-spores, or "gonidia," of Lichens that there is in the other groups. There is, however, this difference; the bud-spore of the lower plants consists of a single cell, whereas in the Lichens it is made up of several cells: it is an aggregate, not a unit.

In Hepatica and Mosses the bud-spores are like those of Lichens, but more highly-organised. In the case of the Ferns and Equiseta there are buds very nearly like those of flowering plants, consisting of a number of minute scales, the outer of which remain scaly, and ultimately perish; the inner gradually develop into leaves, while the central pimple of cellular tissue from which these scales emerge lengthens into a shoot, that shoot into a branch, and so on.

Moreover, that bud, if separated and placed under proper conditions, will form a new plant.

In this way the gardener prepares his cuttings. He takes a "slip" with a bud attached, places it in moist earth, covers it with a bell-glass to prevent undue evaporation, and places it in a sufficiently warm locality. After a time the cutting "strikes," as it is termed; that is, it forms roots, which roots absorb nourishment. The cutting is thus truly a chip of the old block. That which the gardener does by art Nature herself often does unassisted. Many Begonias form buds from almost any portion of their surface, and in prodigious numbers, recalling the way in which similar buds are formed on the Mosses, but in even greater profusion. Other illustrations may be seen in the little bulbs which beset the stalk of the tiger-lily, or protrude from the margin of the leaf in Bryophyllum. This process of bud formation occurs also, to some extent, in the animal kingdom, as among the hydras, but is by no means of such general occurrence as in plants.

Under ordinary circumstances all the buds on any particular plant are in all material points alike, and the shoots resulting from those buds are also alike. There are differences in size and vigour and what not, for no two are precisely alike any

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