Jan. 27, 1876] 



NATURE 



249 



observations of the comet of Halley at its appearance in 

 1607 ; his " Development of a general method for calcu- 

 lating the perturbations of comets" from his classical 

 work on the great comet of 1807, published at Konigsberg 

 in 1810, and somewhat difficult to meet with now, in its 

 original form ; the well-known memoir on the physical 

 condition of Halley's comet with the plates, taken from 

 Vol. 13 of the Astronomische Nachrichten ; the memoir 

 presented to the Berlin Academy in 1824, entitled "Un- 

 tersuchung der Theils der planetarischen Storungen, 

 welcher aus der Bewegung der Sonne entsteht ; " re- 

 searches on the Satumian system, the position of the 

 plane of the rings and their dimensions, the figure and 

 dimensions of the planet, the motions of the Huyghenian 

 satellite and determination of the mass of Saturn there- 

 from, and the memoir on the theory of this system from 

 Vol. 28 of the Astronomische Nachrichten ; the Prize 

 Essay " Untersuchung der Grosse und der Einflusses des 

 Vorrucken der Nachtgleichen," to which was attached the 

 motto, " Non frustra signorum obitus speculamur et ortus ;" 

 various papers on precession, aberration, &c., which ap- 

 peared in the Tabula: Re^iomentance, and elsewhere, and 

 the essay on the " Scheinbare figur eines unvollstandig 

 erleuchteten Planeten scheibe." 



The portrait of Bessel after Mandel is prefixed, with 

 reminiscences of his early life, from the correspondence 

 with Olbers, and additional notes by the editor. 



The work is entitled " Abhandlungen von Friedrich 

 Wilhelm Bessel herausgegeben von Rudolf Engelmann, 

 — Efster Band, Leipzig, 1875." 



THE FLOWERING OF SPRING PLANTS* 



DURING the past twenty years the Scottish Meteor- 

 ological Society has been collecting data relative to 

 the budding, leafing, flowering, and defoliation of trees 

 and plants, and to the migrations of birds in connection 

 with the periodical return of the seasons, and it was pro- 

 posed some time ago to discuss the material which has 

 been accumulated. As prehminary, however, to this very 

 difficult line of inquiry, it was resolved to discuss in the 

 first place the observations which have been made by Mr. 

 McNab on the flowering of spring plants in the open air 

 in the Edinburgh Royal Botanic Garden during the past 

 twenty-sbc years, and which have been published in the 

 Transactions of the Botanical Society of Edinburgh. These 

 observations have been made by the same observer on the 

 same plants, growing in the same situations, during the 

 whole of the twenty-six years. 



The average day of flowering of thirty-two spring 

 flowers has been determined, of which the following are 

 examples : — Galanthns nivalis^ Jan. 25 ; Eranthis hye- 

 malis, Jan. 30 ; Hepatica triloba, Jan. 31 ; Corylus Avel- 

 lava, Feb. 2 ; Rhododendron atrovirens, Feb. 3 ; Crocus 

 susianus, Feb. 4 ; Leucojtnn verniim, Feb. 10 ; Daphne 

 Mezereum, Feb. 22 ; Narcissus pumilus, March 10 ; Oro- 

 bus vcrnus, March 11 ; Muscari botryoides, March 18 ; 

 Ribcs sanguineu7n, March 22 ; Narcissus pseudo-Nar- 

 cissus, March 31 ; and Fritillaria imperialis, April i. 



The lateness or earhness of the different springs, as 

 .otermined from the times of flowering of the thirt>'-two 

 plants in each year, is considerable. The latest spring 

 was 1855, which was thirty days later than the average, 

 and the earliest 1874, which was twenty-three days earlier, 

 thus giving a difference of fifty-three days between the 

 latest and earliest springs during the past twenty-six 

 years. As regards particular flowers, the deviations are 

 much greater. The largest deviations from the average 

 dates of flowering occur before the time of the equinox, 

 when deviations of from five to seven weeks either way 

 are of repeated occurrence ; but after the equinox the 



* Abstract of a paper read before the Edinburgh Botanical Society on 

 ™ 13th inst. The paper itself is in type for the Journal of the Scottish 

 Meteorological Society. 



deviations are markedly less, seldom reaching three 

 weeks. 



The springs of 1855, 1856, 1857, 1865, and 1870 were 

 late throughout ; and on the other hand, the springs of 

 1851,1862,1863, 1868, 1869, 1872, and 1 874 were early 

 throughout. Great variations have occurred in other 

 springs, such as 1864, which, being preceded by a very 

 mild December, many spring plants came into flower in 

 the end of 1863, But in January the temperature was 

 2°"o under the average, and in February, 5°'2, and vege- 

 tation was consequently arrested. March was also under 

 the average, and the weather did not improve till April 3, 

 the mean temperature of this month being i°7 above the 

 average. The disturbing influence of this abnormal 

 weather on the dates of flowering was in some cases very 

 great. Thus, Sisyrinchium grandijlorum flowers on the 

 average eleven days earlier than Daphne Mezereum, but 

 in 1864 Daphne Mezereutn did not come into flower till 

 eighty-six days after Sisyrinchium grandifloruni had 

 flowered. It is the occurrence of these disturbances 

 which renders a long series of years necessary in order to 

 arrive at a sufficiently close approximation to the true 

 mean dates of flowering. 



As regards Edinburgh, Jan. 1 1 may be considered as 

 the turning point in the winter temperature, since previous 

 to this date the temperature is, on the whole, falling, and 

 after this date it continues steadily to rise.* Further, 

 after this date the rainfall becomes less, clear weather is 

 of more frequent occurrence, and the increase in the tem- 

 perature is very largely due to an increase of sunshine. 

 The extremely slow rate at which, up to the end of 

 February, the mean temperature rises, and the small 

 differences among the temperatures up to this date, and 

 the large number of plants — fourteen in all out of thirty- 

 two— which come successively into flower during the 

 interval, suggest that it is not so much absolute tempera- 

 ture that calls for consideration as the accumulated 

 amounts of the preceding daily temperatures, in the extent 

 to which these rise above freezing. The accumulated tem- 

 peratures, thus calculated, are, for Galanthus nivalis, 72^7, 

 and G. plicatus, I46°"4 ; for Crocus susianus, 12^°'2, and 

 C. vernus, i79°'i ; for Rhododendron atroviretis, i2o°'3, 

 and R. Nobleanuni, 249°"3 ; and for Narcissus pumilus, 

 347°"o, and N. pseudo-Narcissus, 540°- 1. Similar data 

 prepared for other places, in this and other countries, 

 would be very instructive in showing how far the order of 

 dates of flowering in Edinburgh is observed in other 

 places, and what is the relation of the dates of flowering 

 at each place to the accumulated temperatures at that 

 place, and what modifications are brought about by purely 

 climatic dififerences, particularly as these occasion diffe- 

 rent results as respects the heating and actinic rays of the 

 sun. 



The thirty- two plants, whose dates of flowering have 

 been determined, include three varieties of one species, 

 viz., the blue, white, and red varieties of Scilla bifolia. Of 

 these three varieties the blue flowers first, viz., on ^larck 

 7; next comes the white variety, on March 17; and 

 lastly, the red variety, on March 21, the r^^ being thus a 

 fortnight later than the blue variety. 



An interesting question may in this connection be 

 raised with reference to the relation which the colours of 

 flowers have to the dates of flowering. With this view, 

 our British wild plants have been grouped according to 

 the difterent colours of their flowers and the months in 

 which the flowers usually first expand, the data being 

 taken from Dr. Hooker's " Students' Flora of the British 

 Islands." In classifying the plants, red includes pink, 

 crimson, and scarlet'; and green, all greenish-white, yel- 

 lowish-green, and greenish-purple flowers. Grasses, 

 carices, and other groups, characterised by incon- 

 spicuous floral envelopes, are excluded. The list exa- 

 mined includes 909 species, of which there are 257 with 



* See Prof. Forbes's paper on the climate of Edinburgh, in Trans. Roy. 

 I Soc., Edin., vol. xxii. pp. 348-349. 



