326 



NA TURE 



YFcb. 5 , 1885 



From May 16 till September 4 the temperature in the sun's rays 

 was constantly above the freezing-point (with exception of May 

 22, when this was not the case) ; on June 15 it reached 48 , on 

 the 26th 54 , on July 5, 70 , and on August II, 66°. 



^Observations at Patwlov ik, Russia, Z<>/.£59° 43' 1 



Date, : 

 Feb. 





88 

 91 

 97 

 9i 

 106 

 in 

 109 



Humidity 



% 



75 

 74 



S2 

 76 

 71 



73 

 73 

 66 



65 



It is clear that the influence of the sun's rays increases with 

 higher latitude, because the sun in summer rests above the 

 horizon. 



[uNow we come to the main point, viz. the effect of the direct 

 solar heat on vegetation in the northern regions. 



In Novaya Zemlya the vegetation (consisting chiefly of herba- 

 ceous plants) is, in places exposed to the sun's rays (at the foot of 

 mountains), like an arctic flower-garden, the surface of the soil 

 not being covered with grass as is the case in the temperate 

 regions. The flowers are here of a much greater size than the 

 leaves. In this island, and even in Spitzbergen, the snow dis- 

 appears in summer by the action of the sun from hills exposed 

 to its light ; but on Ben Nevis in Scotland, being a difference 

 in latitude of more than 20°, the snow rests sometimes the whole 

 year. 



In the Tundra of Siberia, on the declivities of hills sheltered 

 from the winds and exposed vertically to the sun's rays, the 

 same herbaceous vegetation, with its large, splendid-coloured 

 flowers, is observed (Middendorff, " Sibirische Reise," bd. iv. th. 

 '• P- 733), but this is not the case in plains where the sunlight in 

 its horizontal direction cannot have so much influence on the 

 vegetation of the frozen ground ; therefore these plains are in 

 general really deserts, only covered with moss. 



Insolation is also the cause of the rich vegetation in some parts 

 of the mountains in the temperate zone (Alps, &c). 



Even in the most northern regions there can be a rich vegeta- 

 tion where the plants in sheltered localities are exposed to the 

 sun. Parry (" Attempt to reach the North Pole") found the 

 scurvy grass (Cochlearia) on Walden Island under 8o° 30' N. lat. 

 in such a luxuriant growth as he had never seen it before. 



Middendorff observed, under 74° 30' N. lat., on the borders of 

 Lake Taimyr in Siberia, on August 2, a temperature of 52° in 

 the shade ; but a heliothcrmometer under glass placed in the 

 sun's rays stood at 104 ; an uncovered one marked, in the sun, 

 70°. The pitch on his boat was not only melted by this tem- 

 perature, but flowed (Middendorff, "Sib. Reise," p. 657). 



But, as is the case also in lower latitudes, the greatest differ- 

 ence between the temperature in the shade and in the sun occurs 

 in early spring. In June, Middendorff was travelling in the 

 Stanowoi Mountains, and saw a rhododendron in full flower ; 

 when he was about to gather some flowers of this plant 

 he found not only the roots, but even the stem, frozen hard 

 in the soil. The temperature of the air was between 54 

 and 43°, but at night it was some degrees below freezing- 

 point. 



The assertion of some botanists that the contents of the cells, 

 as soon as they are frozen, make the latter burst, thus causing 

 the death of the plants, has been already refuted by Nageli ; 

 but the important observations of Middendorff have showed 

 clearly that the severest frosts of the Asiatic cold pole, by 

 which the innermost parts of the trees are frozen as hard as 



Annaten des Physikaliscken Central Ohservntoriums, St. Petersburg, 



iron, have little influence on the tissue when the cold becomes 

 gradually more intense ; only when the temperature sinks sud- 

 denly beiozv the freezing-point if the mercury the wood splits 

 with a thundering n nise. These crevices have a disadvantageous 

 influence on the vegetation of the tree in summer, because in 

 these places the plant often begins to rot. 



The trees rest in a frozen state till, in spring, the sun'- rays 

 reach the upper parts, and here vegetation is raised, though tbe 

 roots and lower parts of the stem are still in a frozen state. 



But the most interesting discovery on this subject was made 

 by Middendorff under 69° 30' N. lat., on April 14, near the 

 village of Dudino ; notwithstanding the clear sky and incessant 

 brilliant light of the sun, the temperature at mid-day ranged from 

 - 4° to - 13°, yet before and after this time from - 24 to - 35°. 

 While going over the glittering snow he was suddenly stopped 

 by the sight of a willow-catkin peeping about an inch out of it. 

 The catkin was wholly developed, yet the branch on which it 

 was observed was, one or two inches clown, solidly frozen ; this 

 was also the case with the other parts of the plant hidden under 

 the snow (Middendorff, p. 653). Thus this little part of a 

 branch was called to life, for some hours only, by the direct solar 

 rays, in which it was thawed. 



In the beginning of August, under lat. 74° 30', Middendorff 

 found the soil exposed to the sun's rays heated to 86°, though 

 the temperature about four inches below the surface was only 

 39°, and at the depth of about one foot the ground was constantly 

 frozen (Middendorff, p. 666). 



It is clear that plants in the high northern regions, when 

 they vegetate, receive more warmth by insolation than is often 

 supposed — 1° by the direct solar light itself, and 2° by the heated 

 surface of the ground. The snow and ice being melted by the 

 sun, the necessa y water and humid atmosphere never fail ; even 

 this is the cause of the luxuriant growth of grass on some places 

 of the Tundra. The flowing water gradually communicates its 

 warmth to the soil, and prevents also the nightly radiation. 



All this is proof enough that, when the mean temperature in 

 shade is known, this is not at all sufficient fir a knowledge of 

 the real temperature by which the vegetation of several plants is 

 raised. What might have been the temperature in the tissue of 

 the little branch and also in that of the willow-catkin, of which 

 we have spoken? and this when the temperature in the shade 

 was so many degrees below freezing-point. 



In the temperate regions vegetation commences in spring, 

 when the difference of temperature between night and day is 

 greatest ; in the high north this difference is often insignificant, 

 because the sun rests above the horizon ; but the temperature of 

 the soil being at this time very much lower than that of 

 the objects exposed to the sun's rays, even this great difference 

 is the cause of the very rapid vegetation in sheltered localities 

 and under thei nfluence of the solar light. 1 



In conclusion we must rem irk that the facts thus briefly men- 

 tioned show how much a new- system of bio-meteorologieal 

 observations is wanted to ascertain the real quantity of warmth 

 and sunlight necessary for the growth of plants, many of which 

 are of the utmost importance in the life of man. 



M. BUYSMAN 8 



T 



NEW ORGANIC SPECTRA" 

 HE absorption-spectra to be described were detected by 

 means of the microspectioscope, and most of them are 

 only fully visible in it, as the dispersion of the chemical spectro- 

 scope is too great for the detection of some of the very feeble 

 bands. A binocular microscope provided with a substage 

 achromatic condenser, to which are fitted two diaphragms, was 

 specially made for this kind of work. Its objectives are so 

 adapted as to enable both fields to be fully illuminated when 

 any power up to the one-eighth is used. The left-hand tube is 

 used as a " finder." and as a means of getting any required 

 portion of the object into the centre of the field so that its spec- 

 trum may be obtained in the spectrum eyepiece of the right-hand 

 tube. In this way the various portions of a very small bit of 

 tissue or organ may be readily differentiated from each other and 



1 In 50 N. lat., on the banks of the Amur River, where the situation 

 willi regard to the ground-ice in spring is the same as in the Taimyr country, 

 Xasiurtiii};: and Cutawaems/is plants were observed to grow about half a 

 foot everyday Nee Beitriige zur Kenntniss des RvssiscJien Retches, Band 

 xxiii. pp. 547, 617. 



3 Abstract of a communication made to the Physiological Society, at the 

 meeting on December 13, 1884 (and published in Proceedings No. iv. 1884), 

 by Dr. C. A. MacMunn. 



