142 



NA TURE 



[December 12, 1907 



most part, collected by members of the Geological Survey 

 in Cape Colony from the Molteno and Burghersdorp beds. 

 The Molteno beds are placed at the base of the Upper 

 Karroo, or Stormberg series ; the Burghersdorp beds con- 

 stitute the uppermost strata of the Middle Karroo, or 

 Beaufort series. Mr. A. L. Du Toit, who has contributed 

 accounts of the stratigraphy of the plant-bearing and 

 associated rocks, describes the occurrence of a transitional 

 zone between the Molteno and the Burghersdorp beds. A 

 description is also given of Schizoneina africana, Feist- 

 mantel, a species originally figured by Hooker in an 

 appendix to Bain's paper, published in 1845. The addi- 

 tional plants recorded from the Molteno beds afford further 

 evidence in favour of assigning- this member of the Storm- 

 berg series to the RhaJtic period. While possessing certain 

 Rhaetic species, the Burghersdorp flora as a whole 

 indicates a sornewhat lower horizon. — Permo-Carboniferous 

 plants from Verccniging (South Africa) : Prof. A. C. 

 Seward and T. N. Leslie. The majority of the speci- 

 mens described in this paper were obtained by Mr. Leslie 

 from a sandstone quarry ih miles from Vereeniging, on 

 the banks of the Klip River ; the sandstones are associated 

 with shales, coal-seams, and glacial conglomerates. In 

 the opinion of the authors, the plant beds should be in- 

 cluded in the Ecca series (Lower Karroo). While recog- 

 nising certain well-marked differences between the Glosso- 

 pteris floras and the Upper Carboniferous and Permian 

 floras of the northern hemisphere, they are inclined to 

 think that there are more types common to the two 

 botanical provinces than is generally supposed. — The 

 structure and relations of the Laurentian system of 

 Canada : Prof. F. D. Adams. This paper contains an 

 outline of the results of the examination by Dr. Barlow 

 arid the author of an area of 4200 square miles, comprised 

 within the Haliburton and Bancroft sheets of the Ontario 

 and Quebec series of maps. The main conclusions reached 

 by the_ author may be thus summarised: — (i) The 

 Laurentian system of Sir William Logan consists of a 

 very ancient series of sedimentary strata, largely lime- 

 stones, invaded by great volumes of granite in the form 

 of bathyliths. (2) This sedimentary series is one of the 

 niost important developments of the pre-Cambrian rocks 

 in North America, it presents the greatest body of pre- 

 Cambrian limestones on the continent, and it is best 

 designated as the Grenville series. (3) The invading masses 

 of granite are of enormous extent; they possess a more 

 or less distinct gneissose structure, due to the movements 

 of the magma, which developed a fluidal and, in the later 

 stages of intrusion, a protoclastic structure in the rock. 

 (4) The granite gneiss of the bathyliths not only arched 

 up the invaded strata into a series of domes, but " stoped " 

 out portions of the sides and lower surface of the arches, 

 the fragments torn off from walls and roof bv the in- 

 vading granite being found scattered throughout the mass 

 of the invading rock; this "stoping," however, probably 

 developed only a small part of the space which the granite 

 now occupies. (5) The invading granite not only exerted 

 a mechanical action upon the invaded strata, "but also 

 gave rise to a variety of metamorphic products, among 

 Others amphibolite, produced by its action in the limestone, 

 which accounts for the fact that while the invaded strata 

 are chiefly limestone, the fragments of the latter, where 

 found in the granite, consist of amphibolite. (6) The 

 invading bathyliths and allied intrusions of granite occuoy 

 the_ gfreater part of the great northern protaxis of Canada, 

 which has an area of approximately 2,000,000 square miles. 

 It has. therefore, been considered advisable to restrict the 

 name Laurentian to this great development of the " funda- 

 rnental gneiss," which, although intrusive into the Gren- 

 ville series, nevertheless underlies and supports it. (7) The 

 relation of the Grenville series, which forms the base of 

 the sedimentary portion of the geological column in eastern 

 Canada, to the Huronian and Keewatin series, which are 

 the oldest stratified rocks in the western part of the pro- 

 taxis, has yet to be determined, the two not having so 

 fT been found in contact ; nowhere, moreover, either east 

 or west, has the original basement on which the first sedi- 

 ments were laid down been discovered ; these are every- 

 where torn to pieces bv the granite intrusions of the 

 Laurentian. 



NO iqSg VOL. yy] 



Linnean Society, Noiember 7. — Ptof. W. A. Herdtnan> 

 F.R.S., president, in the chair. — The origin of the di- 

 trimcrous floral whorls of certain dicotyledons : Rev. G. 

 Henslow. The object of the present paper was to show 

 that the ternary arrangements of monocotyledons are not 

 derived from the same source as those of certain dicoty- 

 ledons, every verticil of three members in the former being 

 a single cycle of the 5 divergence, while in the latter 

 the usually dotihic verticils are derived from the v. This 

 divergence is unknown in the foliage of monocotyledons, 

 n or I being the natural sequence from a single cotyledon, 

 whereas | necessarily follows on the two cotyledons or 

 from opposite and decussate leaves. — Eight very remark- 

 able new species of Acari from New Zealand, from the 

 collection of the late E. Bostock, si.\ Oribatidre and two 

 GamasidEe : A. D. Michael. The species are to be called 

 Oribata bostocki, distinguished by the pteromorpha; being 

 attached to the anterior margin of the abdomen instead 

 of its lateral margin ; Notaspis spiiiulosa, carrying spinu- 

 latod hairs of extraordinary size ; Notaspis caudata, with 

 a posterior projection not hitherto found in the genus ; 

 Hcrinannia phyllophora, with great leaf-like processes on 

 the legs; Nothrus cophinarius and N. iiiigiiifcra, extreme 

 exaggerations of that section of the genus represented in 

 Europe by N. spiniger ; Trachynotus scleropliyUus, in 

 which the great leaf-like transparent hairs found on many 

 Acari have become opaque, hard, brown chltin ; and 

 T. fimbriatus, with singular flattened borders to the first 

 pair of legs, much broader than the legs themselves. — 

 .Eiiigmatistcs nfricainis, a new genus and species of 

 Diptera : R. eiielford. 



November 21. — Prof. W. A. Herdnian, F.R.S., presi- 

 dent, in the chair. — Exhibits. — C. W. Anderson : A speci- 

 men of a light-giving larva brought bv him from near 

 the boundary of British Guiana with Brazil, exhibiting 

 when living a ruby light in its head, and a double row 

 of phosphorescent spots along the body, two on each seg- 

 ment. These lights were not intermittent, but glowed 

 continuously. This presumed coleopterous larva was called 

 " Macadoub " by the natives, and is not uncommon in the 

 region n.amed. — Prof. Dendy : Two living specimens of 

 Peripatus from the Cape, which he had succeeded in keep- 

 ing in excellent health by supplying them with woodlice 

 as food. — Papers. — .Abnormal structures in leaves and their 

 value in morphology : W. C. Worsdell. Dichotomy, as 

 in crested fern leaves, is a reversion to a primitive type 

 of frond-branching. In cotyledons it represents a tendency, 

 which in this case is progressive and not reversionary, to 

 increase the number of cotyledons. Phyllota-xis : Dicho- 

 tomy of foliage leaves is, in the author's opinion, a re- 

 version from the opposite, or distichous, arrangement to 

 form a greater number of leaves on the axis ; it is probably 

 a step towards the original spiral arrangement. Spiral 

 torsion is due to a reversion from the opposite or whorlcd 

 arrangement of leaves to the spiral arrangement. 

 Terminal leaves : This is regarded as a reversion to the 

 primeval structure in which, according to the phyton 

 theory, each leaf terminates each segment of the stem 

 above which it is situated, every leaf being thus essentially 

 a terminal organ .and not lateral. Enations and ascidia : 

 The foliage leaves of Sa.xifraga ligulata show formation 

 of basal pockets on upper side of leaf and transformation 

 of entire leaf into a cup-shaped structure ; also infolding 

 of basal lobes, which infolding may extend right up mid- 

 rib to apex. This infolding may also occur for a short 

 distance from the apex downwards. .\ similar structure 

 may be represented merely by slight enations on either 

 side of the midrib. Lobing may occur at the apex ; small 

 lobes may become abstricted off as stalked structures, 

 which may either be terminal or carried over on to the 

 dorsal (lower surface) of the leaf in form of small, stalked 

 ascidia. Virescence : The various foliar organs of the 

 flower may revert to the condition of foliage leaves, e.g. 

 phyllody of the calyx in the rose, phyllody of carpels in 

 Trifolium. Monocotylcdonous seedlings in dicotyledons : 

 Normal cases of this occur, as in Raniinciihis Ficaria, L. ; 

 here the conditions are regarded as primitive. .Abnormal 

 cases occur in which the two cotyledons arise congenitally 

 fused into a single one, as in Umbelliferae. This is a 

 reversion to the primitive condition. — Two new species of 



