2 86 



NATURE 



{July 20, 



zoospores in motion have a power of contracting and expanding 

 very quickly, and of very considerably changing their form j this 

 changing of form, he considers, constitutes in itself the mechanism 

 of motion. In this essay he has clearly proved that in the alga.- 

 then under examination, the cilia cannot be the true organs of 

 motion. 



The zoospores originate always in the cells that be on or near 

 the margin of the frond ; they afterwards appear in abundance 

 in the upper parts of the frond, whence they spread gradually 

 downwards, till they fill up all the cells of the monostromatic 

 part. 



When the motion finally ceases, the zoospores fasten them- 

 selves to some object near at hand, and then begin to develop 

 into young plants. The zoospores which, till this time, were 

 formed of the bare protoplasm only, are now covered with a 

 cellular membrane. The cilia disappear, and a process of 

 division commences, which, however, in the species of this genus, 

 has not been studied. In several other well-known Ulva;, this 

 division tikes place first in one dimension, but afterwards in 

 two : thus an expanded membrane is formed. This increase in 

 size takes place, according to the observations of authors, 

 principally, but not exclusively, in the periphery of the frond, 

 or on the apex, if there be one. The youngest parts of the 

 plants are thus always at the top, and the oldest at the base. In 

 this way the frond acquires a tolerable leaf-like aspect. 



As before-mentioned, the frond does not in all the species 

 remain attached during its whole life to some object. It is 

 often found, fresh and in full vigour, lying loosely at the bottom 

 of the water in which it grew. Thus, according to the 

 experience of authors, these free examples are entirely mono- 

 stromatic. Hence there is reason for the opinion that, in this 

 case, the frond divides itself into two parts, and that the division- 

 line between them falls just on the border between the upper 

 monostromatic part of the frond and the lower, and not mono- 

 stromatic. The upper part of the frond survives for a consider- 

 able time, and generally increases in size, until the formation of 

 ■ res begins, when it gradually decays. The fate of the 

 other part of the frond is involved in obscurity. Dr Wittrock 

 thinks it not improbable that the cells may detach themselves 

 from each other, and become a kind of fixed gonidia, which 

 finally develop into young plants. Such a mode of increasing 

 would agree with that which, according to Kutzing, occurs in 

 several species of the genus Ulva of authors [Phycoseris, Ktz.), 

 where the cells in the stipes of the plants, after the frond 

 becomes free, put forth budding-cells. It also occurs in 

 Prasiola. 



Kutzing, in his works, speaks of another kind of reproductive 

 bodies, the so-called Spermatid, which he says occur in the 

 Ulvacex. He describes them as brown, and as detached from 

 the surface of the frond, also as round bodies with a thick hya- 

 line membrane, the contents of which are brown and granular. 

 In Ulva latissima, Ktz., to judge from the figure, they appear 

 to be about three times as long as the outer cells. Dr. Wittrock 

 had been unable, after diligent search, to find them. To Thuret 

 their use was unknown, and lessen supposed that they proceeded 

 from some accidental deformity of the common cellular tissue. 



No genu in the whole vegetable kingdom has so wide a range 

 as Monostroma. It has representatives in all parts of the world, 

 but the greater part of the species prevail in the colder parts of 

 the European temperate zone. Of the eighteen species which 

 are known with tolerable certainty to belong to the genus twelve 

 are found in this zone. In the southern part of the Polar regions 

 the genus has not less than seven representatives ; in the equa- 

 zone one species is found; south of the range of the 

 "wild goat," only two. In Europe there arc fifteen species; in 

 Asia, two (or, including M. fuscum, three) ; in Africa, one; in 

 North America, one; in South America, one; and in Australia, 

 three species. 1 



Many of the species grow in salt water, some prefer brackish, 

 others inhabit Fresh water. They grow generally in shallow 

 water, most frequently only one or two feet below the surface ; 

 but two species often grow many fathoms under water. Some 

 species are found at nearly all times of the year, others in the 

 spring ami summer only. All are annuals. 



To facilitate examination and to preserve as much. 

 the natural order, Dr. Wittrock has subjoined a tabular view of 

 the species which he has examined. The characters are here 



1 At present three snecies only of Monostroma are known to grow on the 

 h *h -res, namely, M. hulhsum, M. Grr-.illci, and M. latinimum. 

 The first inhabits fresh water, the others salt water. On the north coast 

 of France five species are found. — M. P. M. 



adduced partly from the form and position of the cells as shown 

 in a transverse section of the frond, partly from the develop- 

 ment of the chlorophyll bodies and the thickness of the frond. 

 The arrangement of the species in this scheme is not altogether 

 the same as that afterwards observed in the treatise. 



The species are fully, even minutely described, and the mono- 

 graph is illustrated by four plates, in which magnified figures are 

 given of the surface and transverse sections of the fronds. These 

 are extremely useful, since the species can be determined by 

 microscopic observation only. Mary P. Merrifield 



SCIENTIFIC SERIALS 



In the most recent numbers of the Journal of Botany (May- 

 July), the most interesting article is perhaps the description of a 

 new British Umbellifer, Selmum Carvi/clia, by Mr. F. A. Lees, 

 illustrated by a plate. The plant is widely distributed on the 

 Continent, and has been now discovered in Lincolnshire by the 

 Rev. William Fowler. It has apparently been confounded with 

 Peucedanum palustre, to which however it is not very nearly 

 allied, and should be looked for elsewhere. 



The recent numbers of the Scottish Naturalist (October 18S1- 

 July 1882) contain the usual supply of articles on various 

 branches of natural history, especially interesting to dwellers in 

 or visitors to the northern parts of our island. 



The American Journal of Science, June. — Respiration of 

 plants, by W. P. Wilson. — On the question of electrification 

 by evaporation, by S. H. Freeman. — Observations on snow and 

 ice under pressure at temperatures below 32 F., by E. Hunger- 

 ford. — On the minerals, mainly zeolites, occurring in the basalt 

 of Table Mountain, near Golden, Colorado, by W. Cross and 

 W. F. Hillebrand. — On a new locality for Hayesine, by N. H. 

 Darton. — Notes on the electromagnetic theory of light, 11., by 

 J. W. Gibbs.— New phyllopod crustaceans from the Devonian 

 of New York, by J. M. Clarke. — An organ-pipe sonometer, by 

 W. Le Conte Stevens. 



The Journal of the Franklin Institute, July. — Descripti a of 

 the Edison steam dynamo, by T. A. Edison and C. T. Porter. — 

 On the efficiency of the steam boiler, and on the conditions of 

 maximum economy, by R. H. Thurston. — Note on the ec momy 

 of the windmill as a prime mover, by A. R. Wolff. — Harmonic 

 intonation of Chime bells (continued), by J. W. Nystrom. — An 

 organ-pipe sonometer, by W. Le Conte Stevens. — Analysis of 

 Helvite from Virginia, by R. Haines. — The absorption of 

 metallic oxides by plants, by F. C. Phillips. — Applications of 

 the principle of the ph.modynamograph, by W. P. Cooper. — 

 Remarks made at the closing exercises of the drawing school, 

 May iS, 1882, by C. Sellers, jun. — Conservation of solar energy, 

 by P. E. Chase. 



The Bulletin of the Torrey Botanical Club for April contains 

 an interesting article by Mr. T. F. Allen on the " Development 

 of the Cortex in Chara," illustrated by 8 plates. The author 

 divides the species belonging to the genus into eight groups, 

 characterised by the mode of development of the cortical cells 

 and cortical tubes. Three new species are described. 



Annalcn a:r Physik uml Cheviie, No. 6.— On the electricity 

 of flame, by J. Elster and H. Geitel.— On double refraction in 

 glass and sulphide of carbon produced by electric induction, by 

 H. Brongersma. — On measurement of small electric resistances, 

 by C. Dieterici. — Note on weakly magnetic and dia-magnetic 

 substances, by P. Silow. — Some experiments on diffusion of 

 gases through hydrophane of Czernowitza, by G. Hufner.— 

 General formulae for determination of the constants of elasticity 

 of crystals by observation of the flexure and drilling of prisms, 

 by W. Voigt. — On the molecular attraction of liquids for each 

 other, by P. Volkmann. — Reply to the memoir of Herr V. v. 

 Lang: "Determination of the quotients of refraction of a con- 

 centrated solution of cyanin," by C. Pulfrich. — Experiments |on 

 colour-mixtures, by R. Schelske. — A proof of Talbot's proposi- 

 tion, and remarks on some of its consequences, by 1 

 On the replacement of a centred system of refracting spherical 

 surfaces by a single one of this kind, by F. Kessler. — On singing 

 condensers, by W. Holtz. — On coloured sparks and their produc- 

 tion by internal and external resistances, by the same. — Remarks 

 on the production of Lichtenburg figures, by K. L. Bauer. 



No. 7.— On transpiration of vapours (III. Memoir), by V. 

 Steudel.— On the same, (IV. Memoir), by L. Meyer.— General 

 formulae, &c. (continued), by W. Voigt.— Volume and angular 



