April 1, 1891.] 



KNOWLEDGE 



65 



that the larger disc-like nummulites are lentils left by the 

 builders of the pyramids, and subsequently turned into 

 stone. From the Caucasus and Asia Minor the Nummu- 

 litic Limestone may be followed into Persia, Baluchistan, 

 Sind, the Punjab, and so into the Himalaya. Thence 

 it continues into Assam and Burma, and reappears in the 

 Andaman and Nicobar Islands in the Bay of Bengal. 



It is, however, in the inner Himalaya that the oceiir- 

 rence of Nummulitic Limestones and certain overlying 

 Tertiary rocks is of more especial interest, since it is there 

 that they attain a greater elevation tlian in any other part 

 of the world. It is in the upper Indus Valley, in the 

 neighbourhood of Leh in western Tibet, that these 

 nummulitic rocks occur ; running some distance down the 

 Indus to the west of Leh, and to the eastward of that 

 town extending into Chinese territory. There is good 

 evidence to show that the arm of the sea in which these 

 nummulitic rocks were deposited communicated with the 

 ocean to the eastward in the Bay of Bengal, instead of 

 foUowing the course of the Indus in a westerly direction 

 to the Arabian Sea. Moreover, in some parts of this 

 area the rocks which overlie, and are, therefore, newer 

 than the Nummulitic Limestone, are raised to the 

 stupendous elevation of more than 21,000 feet above the 

 sea-level. 



We have, therefore, before us decisive evidence to show 

 that those parts of the earth's surface which at the present 

 day form some of the highest peaks in the Himalaya were, 

 at the period when the London Clay was deposited, below 

 the level of the sea ; and consequently that the elevation 

 of that part of the Himalaya has taken place entirely 

 since that epoch, during a period when the physical 

 features of England have altered only to a comparatively 

 slight degree. There is, moreover, equally conclusive 

 evidence to show that the elevation of the Himalaya was 

 not completed until a much later epoch of the earth's 

 history, since on the southern flanks of this mighty range 

 we find beds of sandstone containing remains of mammals 

 which lived during the Pliocene, or later Tertiary epoch, 

 raised to a height of several thousand feet above the sea- 

 level. 



The elevation of the Indus Valley in the heart of the 

 Himalaya could not, therefore, have commenced until the 

 Miocene, or middle Tertiary epoch, while that of the outer 

 Himalayan ranges could not have been completed till far 

 into the Pliocene period, and, for all we know to the 

 contrary, may still be in progress. Not only so, but the 

 same endence likewise tells that the Alps, Pyrenees, 

 Carpathians, the Caucasus, and the Egyptian Mokattam 

 range, as well as the moimtains of Algiria, have all 

 attained their present elevation since the latter part of the 

 Eocene period, when at least a considerable portion of 

 their area was submerged. And we accordingly learn that 

 many of the most striking physical features of the Old 

 World are of comparatively modern origin. 



When, however, we turn to mountains like those of the 

 Lake District and Wales, which only attain moderate 

 elevations, and in which the rocks belong solely to the 

 Palipo/.oic, or oldest geological epoch, it is evident that we 

 have to do with elevations of an extremely remote date. 

 There is, indeed, satisfactory proof that these old moun- 

 tains were once vastly higher than they are at present ; 

 their diminished altitude being due to the long ages during 

 which they have been subjected to the wear and tear of 

 the elements. To such mountains the proverb to which 

 we have already alluded is, therefore, strictly applicable ; 

 but in a geological sense the phrase " everlasting hills " 

 can be applied neither to the oldest nor the yomigest 

 mountains. 



DISSEMINATION OF SEEDS. 



By Theodore W. Dicker. 



THE dispersion of seeds over the wide surface of the 

 globe, which has been of so much importance in 

 the distribution of vegetable life, has been accom- 

 plished by adaptations as marvellous as they are 

 oft'ective. In these methods we find another 

 proof of Nature's firm determination to carry on the race. 

 Fhst we have the astonishingly la^•ish manner in which 

 seeds are produced. Eight thousand have been coimted 

 in a single capside of the White Poppy, whilst it has been 

 estimated that a single Tobacco-plant can produce 860,000. 

 How multitudinous, too, are the microscopic spores of the 

 Flowerless Plants. It has been calculated that a single 

 frond of Spleenwort could produce a million spores, and 

 it is necessary to only shghtly kick a mature Puff-ball 

 (Lycoperdon) to drive the spores out in a small cloud. 

 Why, then, it may be asked, with all this tremendous re- 

 productive potency, is not the earth overrun to a most 

 inconvenient extent by plant-life ? The possibiUty of over- 

 production is checked in many ways, among which are 

 the unsuitability of position, the destructive struggle for 

 existence which goes on among crowded plants, and by 

 the great consumption of seed by men and the lower 

 animals. 



In addition to the exuberance of production we must 

 take into consideration the power which seeds and fruits 

 possess of resisting injiny. They are less perishable than 

 any other part of the flowers producing them, and are well 

 adapted to retain their vitality, even through great changes 

 of temperature, for a length of time. Some wheat which 

 Sir George Nares brought from the Arctic regions, where 

 it had been left by the crew of the i'ularis two years before, 

 was found to still possess its germinating power ; and 

 Dr. Trimen states that some seeds of ^felumbium in 

 the herbarium of Sir Hans Sloane, who died in 1753, 

 germinated in 1866. 



In the distribution of seeds we find three kinds of 

 agencies concerned, sometimes acting independently and 

 sometimes in concert. First, there are the remarkable 

 efl'orts which plants themselves make to disseminate the 

 products of fructification ; secondly, there is the powerful 

 instrumentality of two inanimate forces without, viz. wind 

 and water ; and, lastly, there is the unconscious but in- 

 terested action of animal life. 



Let us examine first the methods by which plants them- 

 selves seek to insure the proper disposal of their seed. 

 Dissemination generally beguis at the close of life in 

 annual plants, and at the " period of rest " in woody 

 plants. It is then, except in the case of succulent fruits, 

 that the fruit attains the degree of dryness necessary for 

 the lil)eration of the seed. Indeed, fruits may be roughly 

 divided mtodry and succulent. As succulent fiuits generally 

 exhibit no particular mechanical efl'orts in themselves at dis- 

 semination, it is with the former, or dry fruits, that this 

 part of our article is concerned. Dry fruits, again, may be 

 separated into the tle/iisvent, or those in which the peri- 

 carps, or seed-cases, open to permit of the escape of the 

 contained seeds, such as the Pea-pod, and the imhltistttit, 

 or those in which the pericarps do not open. Taking first 

 the ileliisceut fruits, we find that they usually consist of a 

 number of seeds enclosed in tough pericarps, as in the 

 Poppy or the Vetch. As such fniits present no special 

 attraction to animals, the seed-cases must of necessity open 

 to permit of the exit of the seeds ; for whei-e the seeds 

 are numerous it would manifestly be to their disadvantage 

 if the fruit merely fell to the earth and they escaped 

 only through the rotting of the seed-case, as this would 



