September, 1902.] 



KNOWLEDGE, 



211 



ivinains collected. But drier ground was near at hand, 

 for with these, seeds of some of our most familiar waj side 

 plants occur — the ubiquitous Chickweed, Buttercups and 

 Violets, and that 



" Dear common fli)wer, that grow'st beside the way, 

 Fringing the dusty road with harmless gold. 

 First pledge of blithesome ifay." 



— the Dandelion. But the flora is distinctly northern, and 

 the Arctic plants are indicative, says Mr. Bennie, of a 

 climate 2i)' Fahrenheit colder than at present — a climate 

 that would allow the Glacial Period to reisn supreme. 



At Hailes, not far away, two plant-beds were found.* 

 T he lower, resting directly on the Boulder clay, yielded a 

 fli>ra with arctic Willows, resembling that just described. 

 Above this lay silts which yielded quite an extensive flora 

 no longer arctic and stunted, but consisting of temperate 

 jilants, such as now occupy the country — Oak, Fir, Hazel, 

 Birch. Alder. Black-thoni. and Bird-cherry ; King-cups 

 and Catchflies, Wood-sorrel, Meadow-sweet, Valerian, 

 Eed-rattle, Clipsywort, Bugle, Mercury, and Dock. 



The white lake-marl, which underlies our bog, and which 

 we have seen to overlie the glacial plant-bed at Cor- 

 storphine, is a deposit widely spread in our islands, and 

 frequently met with. The passing away of the ice left 

 the country strewn with ridges and mounds of clay and 

 gravel, which, interfering with the old drainage, conduced 

 to form numerous lakes and pools. And as the country 

 Ix'came again clothed with trees and herbaceous vegetation, 

 the waters also were colonized by an abundant flora, which 

 advanced from the south as the ice retreated further and 

 further northward. Among the plants which flourished 

 were (piantities of Characew or Stoneworts, many of which 

 have their stems habitually encrusted with lime, whenever 

 a sufficiency of lime is dissolved in the water. Various 

 plant-eating water-snails swarmed in these pools, and also 

 water-fleas or Eutomostraca, which have calcareous tests. 

 As generation after generation of these plants and animals 

 came and went, their limy crusts or shells fell to the 

 bottom of the pools, and by degrees formed these white 

 beds of marl. The process may still be seen in actual 

 operation. Mr. Skertchly foundf that the evaporation of 

 the water in the ditches of Burwell Fen during the ex- 

 cejitional drought of 1874 left a white deposit of Chara 

 remains from two to four inches in thickness. If a sample 

 of this white marl be examined carefully, the roots and 

 seeds of Chara may almost always be found, and there can 

 be little doubt that plants of this genus largely contributed 

 to its formation. The conditions under which a deposit of 

 the kind would form are such as still obtain around our 

 bog. First, the water must be charged with carbonate of 

 lime — in the great limestone plain of Ireland it is difficult 

 to find water that is not ! The water must be clear, for 

 Charas do not favour muddy pools ; and the pools must be 

 of moderate depth. To judge from the wide range of 

 these marls, such conditions must have been frequently 

 fulfilled in the post-Glacial lakes. The marls are ])oor in 

 plant-remains in general. The still clear waters in which 

 they were formed would not receive seeds and fragments 

 of the shore vegetation in the ordinary course, as would a 

 turbid pool through which a stream ran : and the material 

 itself is far less fitted to preserve plant-remains than beds 

 of fine silt. Nevertheless, in a sample of the marl taken 

 not very far from the spot where we now in fancy stand, 

 Mr. Clement Iteid found+ seeds of Water-buttercup, 



• Clement Reid : " Origin of the British Flora," p. 72-74. 1899. 



t JUeiii. Geol. Survei/ England and Wales: Geology of parts of 

 Cambridgeshire and o/Suffolk, pp. 98, 99. 1891. 



X " On tlie Origin of Migaceros-marl." Irish, Naturalist, IV., pp. 

 131, 132. 1895. 



Milfoil, Shore- weed. Club-rushes, Sedges, and two Pond- 

 weeds, all being plants, it will be noticed, that would grow 

 in the pool or on its edges. Water-snails, which delight 

 in clear limy waters, were abundant in these old lakes, 

 and their shells sometimes form a considerable portion 

 of the deposits. Several species of Limniea, Succinea, 

 and Valvata are often present in numbers, and also repre- 

 sentatives of the genera Sphxriiun, Planot-bis, Phijsa, 

 Bythinia, Pisidinin, &c., all being species which are still 

 abundant in our ponds ; so that the fossils, both vegetable 

 and animal, point to a climate hardly distingui.shal)lc from 

 that which now obtains, and to a flora and fauna closely 

 resembling the present. One characteristic fossil of these 

 Irish marls has, however, yet to be mentioned. It is in 

 these deposits rather than in the peat which overlies them 

 that the remains of the Great Irish Deer, Cervus giyanteua, 

 commonly known as the Irish Elk, occur, often in surprising 

 quantity. This splendid animal stood as much as 2l 

 hands, or 7 feet high, and its antlers measured 10 feet 

 or more across ; it attained an abundance in Ireland 

 unequalled elsewhere in its range, which stretches chiefly 

 over northern Europe (though reaching as far south as 

 Italy) into Siberia. In the old bed of one small lake 

 among the hills of County Dublin, over one hundred heads 

 have been obtained. Appearing in these countries after the 

 Great Ice Age, this noble animal must have been roaming 

 the plains in thousands at the time when the slow accumu- 

 lation of limy sediment was forming these white marls ; 

 ere the forest period which succeeded had arrived, the 

 Great Deer had vanished from the face of our planet. 



Thus have we briefly sketched, by means of the plant- 

 remains embedded in contemjiorary deposits, the history 

 of the flora of our country, from the repeopling of the land 

 on the departure of the ice to the time when many of the 

 lakes which formed on the surface of the Boulder clay had 

 silted up. Immediately overlying the white marl in the 

 turf cuttings of our bog are the lowest layers of the peat 

 which rises full thirty feet in thickness. The history of 

 the bogs — their birth, life, and death — must form the 

 theme of a subsequent chapter. 



COLLECTING, PRESERVING, AND 

 MOUNTING ALG>E. 



By Henry J. Foster. 



Many microscopists would be glad to be acquainted with 

 the best methods for collecting, preserving, and mounting 

 as microscopical specimens, the beautiful varieties of marine 

 and fresh-water Algaj, and the information that it is here 

 proposed to give will, it is hoped, enable this to be done. 



It will be found desirable to combine both the marine 

 and fresh- water varieties in collections, for in their 

 botanical arrangement according to structure and modes 

 of growth, the steps in the scale of nature towards higher 

 forms are independent of the accident of habitat. The 

 exquisite structure, differing in every species, causes these 

 subjects to be of especial interest to the microsco])ist, and 

 that interest is immensely increased when he has collected, 

 prepared, and mounted the specimens for himself. Although 

 it is eminently desirable that classification and nomen- 

 clature should be attempted, it is of course not an essential ; 

 but there is little doubt that preliminary observation will 

 ultimately lead to fuller investigation, and perhaps to real 

 study. 



Marine Alga;. — If the collection of these specimens 

 is to be an object in a visit to the seaside, it will be well 

 to choose for preference a rocky and perhaps somewhat 

 bleak coast, where there is an abundance of rock pools. 



