December i, 1910] 



NATURE 



139 



to whether bay-dun or bay or dun better describes the filly 

 (1907) by Ash (chestnut) out of Unexpected (bay). Here, 

 however, is another instance of reversion to dun which 

 has come under mj' personal notice, viz. bay-dun hackney 

 filly (foaled 1898), bred by the late Dr. \V. Wingate Saul. 

 She was by General Gordon, brown (gametic composition 

 brown-chestnut) ; her dam, Fanny Gordon, a light yellow 

 bay with black dorsal band. Fanny Gordon was by 

 General Gordon out of Lancaster Fanny, dark liver- 

 chestnut. J. B. Robertson. 

 Lancaster. 



Lower Cretaceous Angiosperms. 



In the course of my work at the British Museum on 

 Cretaceous plants, I have examined a number of more or 

 less perfectly petrified " woods." Such specimens have 

 generally been classed together as " Gymnosperms," so 

 that they have received little attention from palaeobotanists. 

 .As I am undertaking an exhaustive study of the Cretaceous 

 plants, the keeper of geology has had sections made of all 

 the likely specimens of woods. 



.Among those sectioned are Nos. V. 115 17, V- 5654, and 

 V. 5452. These are of exceptional interest, because they 

 prove to be, not Gymnosperms, but Angiosperms. One of 

 them is further notable in having its phloem and cortex 

 petrified, as well as the wood ; the majority of silicified 

 woods having lost these soft tissues. The specimens were 

 collected at different times, which minimises the chances 

 of error in referring them to the Lower Greensand ; and 

 from geological and petrological evidence there is no reason 

 to doubt that they are, as labelled, of Lower Greensand 

 age {i.e. the .Aptian of the Continent). 



I hope shortly to publish a complete and illustrated 

 account of these specimens, but I make the discovery 

 public now in the hope of obtaining further evidence. 

 Hitherto the floras between the Wealden and Tertiary ages 

 in Britain have not received much attention, owing to 

 the very scanty and imperfect nature of the fossils re- 

 presenting them. Nevertheless, many collectors may have 

 laid aside " wood " from the Greensands, Gault, or Chalk, 

 and, if so, might be willing to lend them to me for 

 examination. 



So far as I am aw^are, the specimens, the nature of 

 which I have recently determined, are not only the oldest 

 Angiosperms from the north of Europe, but are the oldest 

 from any locality with petrified structure. From the 

 succeeding .Albian, Fliche described an angiospermic wood 

 — Laurinoxylon albiense — which he remarked was then 

 (1905) the earliest known petrified .Angiosperm. The 

 numerous Angiosperms described from the United States 

 and elsewhere from the Potomac and succeeding forma- 

 tions are leaf impressions only. 



The existence of .Angiosperms in northern Europe at so 

 early a horizon as the .Aptian is a fact which will necessi- 

 tate revision in some current views as to the early dis- 

 tribution of the most important group of plants. 



Manchester Universitv. ^L C. Stopes. 



The Cocos-Keeling Atoll. 



As a contribution from a frank supporter of Sir John 

 Murray's theory of the formation of the lagoons of atolls 

 by solution, I welcome the criticism of Miss Drummond 

 (Nature, November 24). 



I must, however, point out that the discussion does not 

 concern the question of the power of sea water to dis- 

 solve calcium carbonate, a fact which, so far as I know, 

 is not doubted, but deals with the more special problem 

 of whether this power for solution is the factor which 

 has caused the development of atoll lagoons. 



She has asked me a question, and I think that she 

 has herself given the answer to it. 



Taking the case which Miss Drummond presents, and 

 accepting all her figures, we have the following facts. 

 Normal sea water contains 01 2 gram of calcium carbonate 

 per litre, and will form no precipitate on standing for any 

 length of time. Sea water that contains more than this 

 quantity (i.e. 0-649 gram per litre) will deposit calcium 

 carbonate " in the crystalline form, and the deposition 

 may go on until the solution contains less than is normally 

 present in sea water." 



NO. 2144, VOL. 85] 



In this last case, the saturation of the solution, in fall- 

 ing from 0649 gram per litre to less than that of normal 

 sea water, has passed through a stage at which it is 

 represented by the normal 0-12. Therefore, in this case, 

 sea water containing 0-12 gram of calcium carbonate per 

 litre will precipitate calcium carbonate, and go on pre- 

 cipitating it until it contains " less than is normally present 

 in sea water." This fact therefore negatives the first 

 statement that sea water containing 0-12 gram per litre 

 will not precipitate. What is the factor that determines 

 the precipitation from normal (0-12) saturation in this case 

 when, as Miss Drummond says, sea water when allowed 

 to stand will not precipitate? I would suggest that it is 

 the presence in the solution of the already formed crystals 

 of calcium carbonate — a condition which is also present 

 " in th° interstices of the massive corals in the lagoons." 



F. Wood-Jones. 



Conflicting Dates of International Congresses. 



.At the request of the Swedish geologists, the Inter- 

 national Geological Congress took place this year instead 

 of in 1909. This year was also that in which the Inter- 

 national Zoological Congress naturally fell to be held. 

 Since, for the convenience of university workers, these 

 congresses are usually held at the same time of year, and 

 since they, with their excursions, now extend over a con- 

 siderable period, especially in the case of the Geological 

 Congress, it was almost inevitable that the times of the 

 meetings should clash. This may not aflfect a large 

 number of participants, but it is rather hard on palaeonto- 

 logists, whose interests lie in both camps, and who, even 

 with the aid of the aeroplane, cannot be in two places 

 at once. 



I should not trouble 30U with a complaint about what 

 appeared to be inevitable this year were there not signs 

 of the same difficulty recurring in perpetuity unless pro- 

 test is at once raised. As a matter of fact, the committee 

 of " Palaeontologia Universalis," when it met at Stock- 

 holm, forwarded to the council of the congress a request 

 that this interference should be avoided in future. That 

 protest seems to have been without result. If so, in 1913 

 the palaeontologist will again find himself summoned 

 either by duty or desire to opposite quarters of the globe. 



F. .A. Bather. 



The Megalospheric Form of Ammodiscus uuertus. 



The interesting discovery of the megalospheric form of 

 the above species in some abundance in the North Pacific 

 Ocean, as described by Mr. J. .A. Cushman in Bulletin 

 No. 71, U.S. National Museum, 1910, pp. 73—5, and 

 noticed in Nature of September i, brings to mind the 

 remarkable occurrence of the megalospheric form only 

 {A. tenuis, Brady) in some dredgings off Great Barrier 

 Island, New Zealand, which I described in the Trans- 

 actions of the New Zealand Institute in 1905 (1906). 

 Curiously, the microspheric form was there entirely absent, 

 although Dr. H. B. Brady had previously recorded it from 

 a neighbouring Challenger station, No. 169. The latter 

 author regarded A. tenuis as perhaps a local variety of 

 the better known .4. incertus. Rhumbler suggested that 

 the form was possibly the megalospheric stage of the 

 species, whilst the present writer, noting a large amount 

 of variation in the initial chamber, suggested that a 

 microsphere might be present in forms otherwise to be 

 regarded as .4. tenuis, giving the diameter of the initial 

 chamber in the New Zealand specimens as 100 ^ to 50 fi. 

 Mr. Cushman 's published figure shows an approximate 

 internal diameter of the proloculum as 250 fi, which is 

 nearer to Brady's published figures than to the examples 

 from the Great Barrier Island. I am now convinced that 

 the specimens from the latter locality had abnormally 

 small megalospheres, giving the minima of measurements 

 so far as known. 



A question here arises how to account for the remark- 

 able abundance of Ammodiscus incertus, clearlv of micro- 

 spheric relationship, in fossiliferous strata from the Upper 

 Silurian to the late Tertiarv". With that problem as a 

 suggestion for observant rhizopodists I conclude this note. 



F. Chap-man. 



National Museum, Melbourne, October 20. 



