HARBWICKE'S SCIENCE-GOSSIP. 



I3 1 



whether these hairs assist in producing the tubers I 

 am not prepared to say, but I have little doubt they 

 act as absorbents of nutriment from the soil. I hope 

 to determine this by microscopic examination. As 

 the plant grows older, the thickened string which 

 attaches the new tuber to the parent gets more and 

 more slender, and at length dies away, and the tuber 

 is then in the state of the first diagram, and the office 

 of the plant, in providing for its continuance, being 

 complete, it also dies. Although the plant has 

 numberless blossoms, it seldom seeds. I cannot say 

 why, as the organs appear remarkably well adapted 

 for that purpose, and bees visit the flowers, blossom- 

 ing as it does so early in the year. It may be, that 

 frosts destroy the pollen, but to make up for want of 

 seed, the plant reproduces itself, by forming, in 

 addition to the underground tubers, numberless little 

 ones in the axils of the leaves, which may be seen on 

 the top of the ground by hundreds when the plant 

 has disappeared. I must here again express my 

 surprise that Hooker should denominate these tubers 

 as roots ; roots are not usually thrown off as inde- 

 pendent plants from the axils of leaves. Botanically 

 speaking, these tubers are underground stems ; in fact 

 in growth the interior part of the upper stem is con- 

 tinued to the end of the tuber, by five nerves. At 

 the same time, I do not think it at all a happy way 

 of expressing it ; really it is a bud, exactly as a rose 

 forms a bud at the base of the leaf ; only in the case 

 of the celandine, the plant being herbaceous, it is 

 thrown off. 



In a very old book, I have just found this extract : 

 "These stems (underground) were mistaken by old 

 botanists for roots, and this error is still frequently 

 committed." Hooker seems to perpetuate the error. 

 Withering is rather better, but still he says, " root of 

 oblong tubers, accompanied by fibres ;" he also says 

 "the^ bases of the leaves contain one or two knobs 

 similar to those of the root." How can they then be 

 roots ? 



J. R. Neve. 



Campden, Gloucestershire. 



Dredging in the Menai Straits. — I did not 

 see Science-Gossip in time to reply earlier, but 

 I wish to say in reply to W. J. R.'s question that I 

 think he would find Beaumaris a very suitable place 

 to make his head-quarters at, and that I am sure 

 Mr. Ambrose, who resides in Church Street and is 

 the proprietor of a library, will give him every 

 assistance in his power with respect to works on the 

 Natural History of North Wales, as well as valuable 

 local information on the subject. Mr. Ambrose, who 

 is a very clever man, has written several notices of 

 the place ; and as I resided in the neighbourhood for 

 three years, I know that W. J. R. will find it a fine 

 field for his researches in marine zoology. — Helen 

 E. Watney. 



THE PRE-CAMBRIAN ROCKS OF ENGLAND 

 AND WALES. 



By W. W. Watts, B.A., F.G.S., 



{Continued from fage 82.] 



5 



s 



HROPSHIRE.—l-a. 1S77 Mr. Allport was 

 working in some rocks which had been 

 mapped as intrusive greenstones in Shropshire, 

 when he discovered that they were bedded acidic 

 lavas stratified with beds of volcanic breccia and ashes. 

 Dr. Callaway was working in the area at the same 

 time, and independently came to the same conclusion. 

 He worked from the Cambrians down to the earlier 

 rocks, just as Hicks had done in S. Wales. Two well- 

 marked groups of rocks are to be found in this district, 

 at Lilleshall, Wrekin, Wrockwardine and Church 

 Stretton, and similar rocks have even lately been found 

 west of the Longwynds and in Radnorshire. In the 

 Wrekin the two groups are fairly well developed, and 

 so the hill may be described in some detail. 



It is a N.E. and S.W. range, with four prin- 

 cipal elevations, — the Ercal, Lawrence Hill, Wrekin 

 proper, and Primrose Hill. The oldest rocks are 

 found at the north and south ends ; newer rocks 

 being let down by faults in the middle. The range 

 is faulted on to the Trias on the west side, while on 

 the east successive members of the Cambrian are 

 faulted on to it and on to one another, the lowest 

 being the Hollybush sandstone, like that of Malvern. 

 At the north end, in the Ercal Hill, there is a fine 

 granitoidite, with a great boss of felstone, of the 

 same character as that of the centre of the chain, 

 intruded into it. At the south end, in Primrose 

 Hill, faulted in to the Pebidian series, there is a 

 series of gneisses, b'alleflintas, granitoids, and schists, 

 remarkably like the Malvern rocks. These belong 

 to the Dimetian system. 



Lawrence Hill and the Wrekin proper, in the middle 

 of the chain, are composed of bedded felsite lavas, 

 agglomerates, and ash- beds, sometimes with immense 

 fragments of Pebidian age. The whole is flanked 

 by a quartzite which appears to be faulted on to 

 the other rocks, and is certainly posterior in age, 

 for it contains undoubted fragments of the Wrekin 



felsites. 



Figs. So and 81 indicate the relative positions of 



these rocks. 



Many other exposures of these rocks occur in the 

 vicinity, and the history of those at Wrockwardine 

 has been so well worked out by Mr. Allport that 

 an account of his chief results may not be out of 

 place. The rocks are purple felsites, and contain 

 many curious structures. They have porphyritic 

 crystals of felspar ; they often show lines of viscous 

 flow or fluxion structure, such as is seen in modern 

 slags and lavas : then they contain curious little 

 spheroidal cracks (like the spheroidal structure of 

 basalt on a small scale), called perlites ; and in some 



