April 5, 1894J 



NA TURE 



527 



dream of growing the trees far apart. Pruning off the 

 large branches of isolated pines, which Des Cars says 

 can be safely reduced to half or one-third of their length, 

 provided foliage branches are left above the section to 

 draw up the sap, will not improve the timber of these 

 trees ; nor certainly, as Des Cars says, render them fit for 

 masts and spars, which can only be obtained from the 

 densely-plantedand slowly-grown pine-forests of Northern 

 Europe. 



To return to the treatment proposed for oak trees ; 

 Des Cars will not persuade foresters that large living 

 branches can be pruned off without danger to the future 

 quality of the timber, however carefully the operation 

 may be performed. It is safer to restrict pruning, in 

 the case of oak, to dead or dying branches, or to branches 

 still too young to contain any heart-wood, and which 

 therefore heal up speedily. Broillard, one of the best 

 of French foresters, who has recently written an excellent 

 book 1 on forest management in France, praises the 

 hedgerow oaks of England especially because they are 

 left with their natural crowns intact. If oaks are to be 

 trained, it should be done whilst they are young. Having 

 premised the danger of too great enthusiasm for pruning 

 on the part of inexperienced persons, there can be no 

 doubt that it may sometimes be necessary to prune large 

 branches of neglected roadside avenue trees, which, 

 however, should have been done whilst they were still 

 only formed of sap-wood ; and in such cases, and in all 

 cases of pruning small branches, Des Cars is an ex- 

 cellent guide, and thoroughly explains how the pruning 

 should be effected, his main ideas being to prune close 

 to the stem, and in merely shortening branches to leave 

 a sap-lifter above the wound, to maintain life in the 

 shortened branch. Finally, all wounds should be dressed 

 with coal-tar. For carrying out the work, De Courval's 

 strong heavy pruning hatchet is recommended, and the 

 use of the saw deprecated, as requiring much practice to 

 use skilfully ; but it is better only to employ skilful 

 woodmen to prune trees, and then the saw is generally 

 the better instrument to use. 



"Webster's Practical Forestry" is another useful little 

 book, giving the experience of a practical man who has 

 devoted his lifetime to the every-day duties of a forester. 

 It is not, however, by any means an exhaustive treatise, 

 and, curiously enough, not a word is said about pruning ; 

 but the author wisely advises that wherever trees are 

 grown for their economic value, they should be kept 

 •close with an unbroken leaf-canopy, so that the lower 

 branches may be killed outright for fully one-half the 

 length of the stems. 



Nothing is said about coppice or coppice with 

 standards, which are the commonest modes of growing 

 woods in England. 



The efficacy of drainage on forest growth is too much 

 insisted on, while the opinion of French foresters on 

 moisture in the soil may be summarised as follows from 

 Broillard's book, already quoted :— 



Dry lands will only produce timber under dense growth 

 of shady trees, which keeps the soil somewhat moist in 

 summer. 



Soils which in summer never dry below 6-8 inches 



^1 " Le traitement des bois en France," par Ch. Broillard. ancien pro- 

 esseur a I't^cole forestiere. (Paris : Berger Levrault et Cie, 1894.) 



xo. y2 75, VOL. 49] 



allow most forest species to thrive. Moist soils, which 

 when pressed in the hand always leave some trace of 

 moisture, are the most fertile, and suit the pedunculate 

 oak, the ash, and the elm. 



Wet soils, usually saturated with water, provided the 

 latter is in movement, and therefore aerated, as along the 

 banks of watercourses, suit alders, willows, and poplars. 



Marshes are usually unproductive, but they afford 

 moisture to neighbouring lands, and fine trees are found 

 along their borders. Thus drainage is only required 

 where there is not enough fall of the ground for the water 

 to move about, and, provided the water does not stagnate 

 the roots of forest trees are the best drainers of a soil. 



Webster gives some useful notes on trees adapted for 

 various soils and for town planting, and ranks the 

 maiden-hair tree {Ginkgo bilobd) and Ailanthus glatidu- 

 losa next to the plane as trees flourishing in spite of 

 the smoke of large cities. He also gives an excellent 

 list of trees adapted to grow exposed to sea-breezes, 

 of which Finns Laricio is the best among conifers, and 

 Norway maple and sycamore among broad-leaved trees. 

 The larch, it appears, when grown on gravel generally 

 becomes rotten at the core, and Webster's advice to 

 study the relationship of trees and soils is greatly needed in 

 England, where it is frequently the practice to plant alter- 

 nate lines of spruce, Scotch pine, larch, and beech without 

 any regard to the different demands they make on the soil. 

 His complaint of preferential railway rates to foreign 

 growers, which have rendered osier-beds unremunera- 

 tive, points to a great obstacle to forestry in the United 

 Kingdom. An Irish land-agent recently said that it was 

 impossible to send wood from the interior to the ports at 

 a profit ; and if our railways cannot provide cheap goods 

 carriage, it is time that canal extension on a large scale 

 were proposed for the transport of our heavy country 

 produce, and that existing canals were withdrawn from 

 the control of the railway companies. 



W. R. Fisher. 



RECENT RESEARCHES ON SACCHARO- 

 MYCETES. 

 Micro-Organisms and Fermentation. By Alfred Jor- 

 gensen (Copenhagen). Translated from the third 

 edition in German by A. K. Miller and E. A. Lenn- 

 holm, and revised by the author. (London : F. W. 

 Lyon, 1893.) 



THE development of bacteriology is closely linked 

 together with the advances made in our knowledge 

 of fermentation, which was first placed on a truly 

 scientific basis through the far-reaching investigations of 

 Louis Pasteur in his "Etudes sur la bi^re." He propounded 

 the doctrine that every fermentation and putrefaction is 

 caused by micro-organisms. This is an accepted theory 

 now, if by fermentation we understand alcoholic fermen- 

 tation. For there are other processes of fermentation 

 which are produced by unorganised substances, whose 

 chemical nature is as yet undefinable, such as ptyalin, 

 pepsin, trypsin. The part played by micro-organisms as 

 ferments in disease is still shrouded in mystery. At one 

 time it was thought that they produce a specific lesion by 

 means of basic bodies allied to the vegetable alkaloids, 

 but differing from them in chemical composition and 



