292 



NATURE 



\yuly 28, 1 88 1 



Nachrichten has not considered it was necessary to reprint it 

 in that journal, where the ephemerides for previous appearances 

 have always found a place. 



After the death of Dr. von Asten, the calculations for this 

 comet were taken up by Dr. O. Backlund, who has continued 

 the computation of the perturbations liy Venus, the Earth, Mars, 

 Jupiter, and Saturn from 187S to 18S1, taking account also of 

 the effect of the to-called resisting-medium on the mean motion 

 and angle of excentricity. The following are the elements of 

 the comet's orbit : — 



Epoch 18S1, July 2-0 M.T. at Berlin 



319 26 487 



158 30 S'S 



334 34 3'i 



12 53 0-3 



57 43 3075 

 io72"-65852 



M.Eq. 

 i8Si-o. 



o'343oi 

 4-09709 

 l2o8'2i days 



Mean anomaly 



Longitude of perihelion . . . 

 ,, ascending node 



Inclination 



Angle of excentricity 



Mean daily sidereal motion 



From these elements we find — 

 Semi-axis major ... 2'220o5 1 Perihelion dist. 

 Semi axis minor ... l'iS547 Aphelion dist. 

 Excentricity o '8454969 | Period 



The track of the comet in the heavens at this appearance is a 

 favourable one for observation in this hemisphere. It will be 

 nearest to the earth on October 11, when it will be distant 0*543 

 of the earth's mean distance from the sun, and situated in the 

 constellation Leo Minor, in the vicinity of the star Fl 21, and 

 the theoretical intensity of light will attain a maximum on 

 November 9, when the comet situated near 89 Virginis will rise 

 about 2h. 15m. before the sun. 



The following ephemeris for the month of August is con- 

 tracted from die accurate one given by Dr. Backlund, and 

 applies to mean midnight at Berlin : — 



RA. 



Decl. 



August 



-1-26 31-0 



27 0-3 



27 30-2 



28 0-7 



28 31-9 



29 3-9 



29 36-6 



30 10-2 



30 44-5 



31 19-8 



31 56-0 



32 33-1 



33 11-2 



Zi 50-2 



34 30-3 

 + 35 "'3 



It remains to be seen whether the comet can be perceived with 

 the larger telescopes of the present day ^vith a less intensity of 

 light than 0-24, which was that at the time of its discovery in 

 August, 1S48, with the 15-mch refractor at Harvard College, 

 U.S., and which will correspond to about the day of new moon, 

 Aagust 24. 



Comet 1881 c — Elements of this comet have been published 

 in cu-culars isued from Lord Crawford's Observatory at Dun 

 Echt, from which it appears that it will increase very consider- 

 ably in brightness. The perihelion pass.ige does not take place 

 until August 21. Ihe comet is rapidly approaching the earth. 



BIOLOGICAL NOTES 



On some New Lower Green Alg.-e. — George Klebs i ub- 

 lishes some very interesting facts about a number of forms of 

 green Algae found living within the cell-tissues of some flower- 

 ing-plants. The painstaking way in which the life-history of 

 these have been worked cannot be too sufficiently admired. 

 For full details the student should refer to the numbers of the 

 Botanisclu Zciliing for April and May, where also will be 

 found excellent coloured illustrations of all the species. In 

 order to call attention to these curious species we give the 

 specific diagnosis in detail : — Family rmtococacea:. Genus Chlorc- 

 chytruiiii. — Through continued division into two parts each cell 

 becomes resolved into spherical zoospcres, which upon leaving 

 the mother-cell conjugate within the gelatinous envelope. The 



zygozoospores before becoming surrounded with a membrane 

 make their way by means of processes into the intercellular 

 spaces of living plants. During the time favourable for vegeta- 

 tion many generations fellow one another in a single year ; that 

 nearest to the « inter falls into a resting stage. Chlorochytriuiii 

 Icmiue. — 1 his species lives in the w idened intercellular spaces 

 of the parenchyma of the Leimia tiisulca : cells chiefly spherical 

 or elliptical ; the part of the growing zygospore which remains 

 in connection with the epidermis becomes a spherical cellulose 

 plug. In the next genus, Endospha:ra, through continued divi- 

 sion into two, each cell falls into a number of daughter-cells 

 surrounded with a membrane, from h hich, by iurther division, the 

 spherical zoospores result ; those, taking their origin from the 

 same mother-cell, immediately upon leaving it conjugate ; they 

 make their way into living tissues like those of the Chloro- 

 chytriuiii. The formation of zoospores only takes place in the 

 spring ; the new generation requhes a full year to reach maturity. 

 The species Endosphixra biennii lives in the intercellular spaces 

 of the sub-epidermal parenchyma of leaves of Fotamo'^eton litcens: 

 its cells are mostly spherical ; the part of the germinating zoo- 

 spore which remains in connection with the epidermis soon dies 

 off. In the genus Phyllobium at the time of maturity, the 

 protoplasm of every cell containing chlorophyll is differentiated 

 into cylindrical or spherical portions, through the changing of 

 some of these into smaller ones, zoospores — both macro and 

 micro are formed — these conjugate. The zygozoospores make 

 their way into the stomates of partly living, partly dead 

 leaves of phanerogams. The development of every cell takes 

 a year. The species Phyllobiiiin diinorphum lives in the leaves 

 of Lysimacliia mimmularia, Ajuga, Chlora, &c. ; the zygo- 

 zoospores develop processes which grow into branched green 

 tubes among the vascular bundles belonging to the veins of the 

 leaves. The protoplasm of those zygospores which develop a 

 process forms into either a spherical or longish resting cell, which 

 lasts during the winter, and in the next summer again develops 

 zoospores. According to the surioujiding circumstances the 

 processes are well developed or n it. They may be (juite rudi- 

 mentary, in which case small tubele.-s resting cells become 

 formed, w hich form asexual zoospores. In the genus Scotino- 

 spha;ra every cell shows at the time of maturity a differentiation 

 of its green protoplasm into cylindrical or spherical bodies ; by 

 their conjugating, during which a reddish granular substance is 

 secreted, a single mass is formed, through w hose repeated divi- 

 sion, during which division the granular substance is gradually 

 again tal.en up, the zoospores are forme '. These are asexual, 

 and make their way into decaying vegetable tissues. Their 

 development lasts a year. Scotirwsphivra paradoxa lives in the 

 dead or dying tissues of Lanna trisulca, and also in species of 

 Hypnum. Its cells are mostly spherical, and tl e zoospores are 

 spindle-shaped. [Botanische Zeitun^, May 27, 1S81.) 



On the Influence of Intermittent Illumination on 

 THE Development of Chlorophyll.— Dr. Karl Mikosch 

 and Dr. Adolf Stohr publish the result of their ii.vestigations 

 m.ade in the Physiological Institution of the Vienna University. 

 The re-ults of these they sun.marise as follows : — If a continuedly- 

 lasting 2 -5-niinutes illumination of etiolated seedlings of barley 

 or oats is compared with an intermittent illumination in the rela- 

 tion of I : I lasting five minutes, then one will find that in both 

 cases the light is throughout present an equal time. Now if the 

 chlorophyll-formation takes place at the same time as the illumi- 

 nation, then the working of the continued illumination must 

 exactly correspond at the end of 25 minutes with the sum of the 

 single effects of the intermittent illumination. As a matter of 

 fact, however, at the end of the continued illumination there has 

 been either no chlorophyll formed, or at any rate no quantity of 

 it that can be pointed out anywhere. On the other hand, the 

 mass of chlorophyll which is formed during the intermittent 

 illumination is beyond doubt capable of being pointed out with 

 a spectroscope. One must therefore imagine that a certain time 

 elapses between illuojination and chlorophyll-formation. From 

 this however it follows : — i. That the chlorophyll-formation is a 

 ] rocess of photochemic induction. The first trace of chloro- 

 phyll that can be pointed out with a spectroscope ajipears in 

 seedlings of barley and oats grown in the dark after illumination 

 lasting five minutes ; it is a matter of indifference whether it is 

 illuminated the whole time through, or only in the relation of I : I 

 second. One cannot take for granted that in the one case only 

 the half quantity of chlorophyll is formed when an alcoholic 

 solution even shows the absorption lines of the chlorophyll 

 spectrum, still this will clearly disappear if the solution is made 



