June S, 1883.] 



SCIENCE. 



523 



occur if insect visits fail. These are found only in 

 groups where specific distinctions are not well marked. 



In completely heterogone species, the differentia- 

 tion extends only to the relative length of stamens 

 and pistil, or it may include the direction of the short 

 styles, which diverge so much as to bring the stigmas 

 in contact with the perianth, or even the length of 

 the stigmatic rays and the form and pubescence of the 

 style. The colors of the flowers do not stand in any 

 relation with the monomorphisra or dimorphism. Di- 

 morphic species have more conspicuous flowers than 

 their nearest horaogoue relatives, this depending 

 either on the size of the individual flowers or on their 

 grouping in compact clusters. The duration of the 

 several species shows a remarkable connection with 

 the presence or absence of heterogony. The large- 

 flowered, dimorphic species are perennials, while 

 most of the small-flowered, homogone species are 

 annuals. — {Berichte deutsch. hot. gesellsch., 1883, heft 

 2.) w. T. [1040 



Floral evolution in monkshood. — Grant 

 Allen gives a popular account of the flower of Aconi- 

 tum, contrasting it with a buttercup, and showing 

 how symmetry and regularity have been lost, and its 

 blue color acquired, through the advantage derived 

 from the visits of bees favored by these changes. 

 The bilateral structure, and the suppression of the 

 lower three petals, are connected with the lateral 

 position of the flowers on the axis of inflorescence ; 

 while the reduction in the number of carpels, and the 

 inci'ease in the ovules, secure the production of as 

 much seed from a single visit of a bee as the butter- 

 cup secures from numerous visits of the mixed group 

 of insects to which it is open. The differences in 

 the relative position of the essential organs during 

 anthesis would also have proved very interesting in 

 this connection. — [Knowledr/e ; Pop. se. moiithly. 

 May.) w. T. [1041 



The relation of the tension of the bark to 

 the formation of annual rings in wood. — It is 

 stated in several text-books, that, owing to the slighter 

 pressure exerted by the bark in the spring, wider 

 wood-cells are produced than at a later period, when 

 the pressure is considerably augmented. Experi- 

 ments by De Vries certainly can be interpreted in 

 this way. Krabbe has recently investigated the sub- 

 ject in a somewhat different manner, and has arrived 

 at a different conclusion. It cannot be said that the 

 subject has yet been settled. It offers a promising 

 field for further work. 



Krabbe's method is the following: strips of bark, 

 not as yet covered with cork, are carefully cut from 

 the stem, and the amount of force required to restore 

 them to their original breadth determined exactly by 

 means of weights. It is well known that such strips 

 of bark shrink at once, and that a considerable force 

 is needed to bring them back to their former size. 

 The tangential tension of the bark increases with the 

 growth of the stem up to the time wlien the corky 

 layer is formed, unless some injury influences the 

 phenomenon. But if we look at the radial pressure 

 (reckoned as the quotient of the tangential tension 

 divided by the radius), it is found that this dimin- 

 ishes with increase of the stem in thickness. Fur- 

 thermore, the radial pressure in autumn is about 

 that of spring, never differing from it more than one 

 gram in the square millimetre; hence being, as 

 Krabbe tliinks, too slight to account for the differ- 

 ence between the spring and autumnal wood. He 

 explains the increase of growth, when pressure is 

 removed by taking off the bark, by the pathological 

 activity following wounds. — (SilzunrjBb. akad. wlss. 

 Ber!., Dec. 14, 1882.) g. l. g. [1042 



Z06'L0GY. 



(General paleontology.) 



Jurassic of Galicia. — In volume v. of the me- 

 moirs of the academy of sciences of Cracovia, Dr. 

 Alth, under the title of the ' Limestone of Nizniow, 

 and its fossils,' describes the recently discovered and 

 very important beds of that locality. From the char- 

 acter of the fossils he refers them to the upper white 

 Jurassic, answering to the united strata of the Kim- 

 meridge and Portland. This work is important as 

 showing the existence of the Jurassic in eastern Gali- 

 cia, where it was formerly unknown, and of great 

 paleontological importance as describing 179 species 

 of fossils, of which 124 are new. Of these, 5 are 

 annelids, 93 gastropods, 57 acephalans, 5 brachio- 

 pods, 2 echinoderms, 6 corals, 6 rhizopods, and 4 

 plants. Curiously, only one cephalopod has been 

 found, the Nautilus Geinitzi. — {Bull. soc. rjeol. 

 i^raiice, Jan., 1883.) j. b. m. [1043 



The sigillarian stumps of Nova Scotia. — 

 One of the most interesting results of the later visits 

 of Sir Charles Lyell to this country was his discovery, 

 in company witli Dr. Dawson of Montreal, of a num- 

 ber of animals entombed in stumps of sigillarians in 

 the coal-measures of Nova Scotia. Dr. Dawson has 

 recently renewed his explorations in the field by aid 

 of a grant from the Royal society of London, and 

 his conclusions have just been published. Up to 

 1876, only three additional trees, of those which be- 

 came accessible by the wasting of the beds, furnished 

 animal remains. But by cutting and blasting, twenty 

 others have now been examined, ten of them proving 

 productive. Dr. Dawson finds that " the circum- 

 stances of the growth and entombment of this forest 

 entirely contradict those theories as to Sigillaria and 

 Stigmaria which suppose that these plants grew in 

 water, or on submerged areas. . . . The surface on 

 which tlie trees grew . . . must liave been underlain 

 by several "feet of peaty matter." The number of 

 terrestrial batrachians found in the stumps has been 

 doutiled by these investigations, additional species of 

 Hylonomus and Hylerpeton having been found, and 

 Fritschia and Sparodus added to the genera, besides 

 a new form called Amblyodon, represented imper- 

 fectly by a few teeth and bones, — making, in all, 

 seven genera and twelve species. Of land-snails, 

 besides Zonites priscus, and Pupa vetusta, found 

 before, another species of Pupa, called P. Bigsbii, has 

 occurred. Of articulates, S. H. Scudder reports two 

 more (unnamed) species of Archiulus, bringing the 

 number of myriapods to six, and fragments of scor- 

 pions — not before recognized — probably belonging 

 to two species. A half a dozen plates illustrate the 

 batrachlan remains. A note is added on the foot- 

 prints of batrachians observed in carboniferous rocks 

 of Nova Scotia, which are referred to six species, 

 equally divided between Sauropus and Hylopus. — 

 {Phil, trans, roy. soc. Lond., 1882, 621.) [1044 



MoUnsksi 



Variations in Unionidae. — Rev. W. C. Hey con- 

 tributes a suggestive paper on the variations observed 

 by him in Anodonta and Unio in the waters of the 

 Ouse and the Foss, and the canals communicating 

 with them, within a very limited area. The point of 

 it is, that, apparently, very slight changes in the 

 environment produce important changes of appear- 

 ance in the moUusks referred to ; though why such 

 causes should produce such effects is not by any 

 means clear. — {Quart, journ. conch., 1882.) w. h. d. 



[1045 



