262 



NATURE [August 24, 1911 



AFFORESTATION IN SCOTLAND. 

 \Y HEN ' a board or council is constituted for promoting 

 afforestation, it is evidently essential that the body 

 should be invested with considerable freedom of action 

 because many of the schemes will present special problems 

 requiring special consideration and localised knowledge. 

 1 he council of the Scottish Arboricultural Society has 

 published as a separate volume (xxv.) of their Trans- 

 actions a report, compiled with great care and labour by 

 Lord Lovat and Captain Stirling of Keir and other ex- 

 perienced authorities, providing a specimen example of a 

 scheme that illustrates very definitely the complex factors 

 that arise for consideration. 



The concrete example presented is situated in the High- 

 land district of Glenmore, Inverness-shire, and has been 

 selected for various reasons, but chiefly because it con- 

 tains wintering land of sheep farms and deer forests, and 

 is also well suited for the creation of small holdings 

 Economic considerations, especially avoidance of an in- 

 creased local rate, occupy a prominent place in the pro- 

 position, and it becomes obvious that the scheme of 

 afforestation, to be financially sound, must fit in with 

 farming and sporting conditions. The nature of the staff 

 and particularly the requirements of the foresters, is a 

 second matter. The sylvicultural problems comprise a 

 working plan stocking of the ground, and utilisation of 

 existing woodland produce. The afforestable land is com- 

 puted at 15,000 acres, of which about two-thirds falls 

 w.thin deer forests and the remainder is sheep ground • 

 according to the proposed scheme, 450 acres would be 

 planted annually for fifteen years, and thereafter ^00 acres 

 per annum. ° 



fl ™fl f tenor , of , the conclusions is to indicate that under 

 a well-framed scheme large areas of land can be afforested 



til, '"A 1 ' ' f ° eX !f ting lnterests ; further ' tha * afforesta- 

 «°"; S rf° Ud f eventuall y Pay its way, besides providing a 

 great deal of permanent and periodic employment. Sug- 

 gestions are also offered with regard to the" nature of a 

 proposed Central Forest Authority for Scotland, differed 

 syst ems of land tenure under afforestati ■ e ™< 



ditions of agreement between landowner and State 



PLANKTON STUDIES ON THE WEST C04ST 



OF SCOTLAND AND IN THE IRISH SEA 

 THE areas in which plankton studies have been carried 

 . on dunn g jecent years in European seas, under the 

 official international scheme of investigation have not 



of fininV h V; e V° aSt ° f Great Britain With Ae view 

 of filling at least ,n part, this lacuna in our knowledge 



d,r n« P Jf" t0n ° f the HHtish area ' Prof - Herdman has, 

 during the years 1907 to 1910, made numerous vertical 



coast SU o fSY If „ fr0 '^ h J S = VaWlt duHn g J U,V 0ff the ™st 

 the risH % t]a "-$i and dun , nfi August and September in 

 the Irish Sea The material collected has been examined, 

 and the results are presented in an interesting account by 

 Prof. Herdman and .Mr. William Riddell » 



In the Irish Sea the phyto-plankton reaches a maximum 



chiefly cLZ y M ^: t , he . sea warming with diatoms 

 (chiefly Chaetoceras, Thalassiosira, and Lauderia) ; then 

 the phyto-plankton gradually dies away, and is replaced 

 by the 200-plankton (copepods, Oikopleura, &c), which is 

 characteristic of the summer months. In September and 

 October diatoms (chiefly Rhizosolenia, Chaetoceras, and 

 Lauderia again appear in profusion, constituting an 

 autumnal phyto-plankton maximum, usually not so marked 

 in bulk or duration as that in the spring. This in its 

 turn dies away, giving place to the scanty winter zoo- 

 plankton— the minimum plankton of the" year— which 

 persists until the reappearance of diatoms in the spring 

 There is thus in the Irish Sea a clear periodicity in the 

 pankton and marked differences in the nature of the 

 plankton of the different seasons. 



Examination of the gatherings made off the wesf coasl 

 of Scotland shows that localities not very far apart differ 

 considerably in the nature of their plankton at the same 

 time of the year. For instance, a vertical haul taken in 

 the Hebridean Sea. off Canna, is a typical fine phyto- 

 plankton, consisting chiefly of diatoms of the genus 



1 Tr.-ins. Biol. Soc, Liverpool, vol. xxv., pp. 60-113, i> figures. 



NO. 2l82, VOL. 87] 



Chaetoceras, whereas a vertical haul, at the same time of 

 the year, at the entrance to Loch Fyne shows a typical 

 coarse zoo-plankton containing large numbers of copepods. 

 This is in marked contrast to the conditions in the Irish 

 Sea, where a zoo-plankton and a phyto-plankton do not 

 occur simultaneously a few miles apart. A list of the 

 Scottish stations is given, with some particulars of the 

 nature of the catch at each, and a detailed analysis in 

 twenty-six cases. The evidence shows that, off the north- 

 west coast of Scotland, at one time of the year (July), in 

 several successive seasons, the plankton was of different 

 types in different localities, but maintained a fairly constant 

 character in each. 



A comparison of the Scottish records with those from 

 the Irish Sea shows that, in species present and in their 

 abundance, the Loch Ranza plankton in July is much more 

 nearly similar to the September than to the April phyto- 

 plankton of the Irish Sea. But the phyto-plankton gather- 

 ings made north of Mull show resemblances to the vernal 

 rather than to the autumnal phyto-plankton of the Irish 

 Sea. There are three possible explanations of the differ- 

 ences observed between the summer plankton of the 

 Hebrides and of the Irish Sea : — (1) the great vernal 

 maximum, which dies away in May and June in the Irish 

 Sea, passes off more slowly further north, and is found 

 lingering, in some parts of the Hebrides, until the end 

 of July, or even longer; (2) in some of the deep northern 

 channels the diatoms, which elsewhere constitute the 

 vernal maximum, persist in comparative abundance 

 throughout the greater part of the year ; (3) the diatoms of 

 the July phyto-plankton may have invaded the Hebridean 

 Sea from the North Atlantic at some period subsequent to 

 the vernal maximum. The authors are inclined, on the 

 evidence available, to regard the first of these suggested 

 explanations as the most likely, but point out that further 

 periodic observations are necessary before the matter can 

 be decided definitely. 



The authors discuss briefly the classification of diatoms 

 into oceanic and neritic species, and give a provisional 

 list of the two categories. A consideration of the phvto- 

 and zoo-plankton shows that the west coast of Scotland 

 is divisible into three well-marked areas, not merely geo- 

 graphically, but by reason of the distribution of its summer 

 plankton : — (1) the Clyde sea-area to the south of, and 

 inside, Cantyre, characterised by zoo-plankton, the species 

 of which are, in the main, oceanic; (2) the area around 

 and to the north of Mull, extending from Cantyre to ihe 

 south of Skye, which contains in July a well-marked phyto- 

 plankton, mainly neritic in character ; (3) to the north of 

 Skye, where a zoo-plankton again appears, which contains 

 some oceanic species. 



The plankton distribution of the west coast of Scotland 

 may be explained in terms of hydrographic movements if 

 it be supposed that Atlantic water gains access more freely 

 in summer to the Clyde sea-area and to the region north- 

 east of Skye than to the large intervening area of the west 

 coast, that is, that an oceanic current reaches the I 

 area and another flows in round the north of Sieve, while 

 little or no such current invades tie area north and south 

 and around Mull. The authors conclude by pointing out 

 that further observations are required in order to deter- 

 mine how far tin- explanation holds good, and also to gain 

 fuller knowledge of the changes in the plankton. I hese 

 changes are hound up with many problems of a funda- 

 mental and far-reaching nature connected with the nutri- 

 tion of marine organisms, and an intimate knowledge of 

 the changes in the plankton is essential to an understand- 

 ing of the movements of the shoals of migratory fishes. 



THE PRUNING OF TREES IN TOWNS. 

 "rill: services of Prof. Bavley Balfour, F.R.S., have been 

 obtained by H.M. Office of Works to inquire into the 

 justness or otherwisi ol complaints made in regard to the 

 treatment of the young trees in the Mall. His report, 

 which 1 1:1 - just been issued from the Stationery Office 

 (Cd, 5823, price 2jd.), must be gratifying to those who 

 have charge of the trees, For he finds nothing to justify 

 adverse criticism of the pruning. On the contrary, he was 

 impress,, I i,\ ih. evidence ol sound practical knowledgi and 



