14 FORESTRY [BoT. Absts., Vol. VII, 



nary, intensively-worked division should certainly not exceed 200 square miles in area, 

 whereas they are now well over 400. The sooner this is recognized, the better." Appended 

 to the report are a number of tables of statistics on forest and administrative subjects. — 

 E. R. Hodson. 



113. Bernbeck. Das Wachstum im Winde. [Growth and wind.[ Forstwiss. Centralbl. 

 42 : 27-40, 59-69, 93-100. 1920. — The author discusses the adaptation of vegetation to wind 

 and the effects of wind on vegetation, with especial reference to forest growth. Adaptation 

 is to enable the plant to withstand the physical impact of wind, or to prevent excessive evap- 

 oration from the plant tissues, or both. Wind firmness is not an inherent characteristic of 

 any given species, although the tendency toward windfirmness may be inherited; thus a fir 

 grown in the open may be much more wind-firm than an oak grown in a dense stand pro- 

 tected from wind. Under the right conditions any tree can develop a wind-firm form. This 

 fact can be utilized in silvicultural management, so as to minimize loss from windfall. 

 (35,000,000 cubic metres of timber, principally coniferous, was blown down in Germany dur- 

 ing the last century.) Wind climate often governs the geographical distribution of trees. 

 For instance, conifers are most liable to injury during the winter months; so sites exposed to 

 continuous winter storms (if fertile enough to allow tall tree growth) are usually occupied by 

 hardwoods, while mountain slopes and plateaus where heavy early summer winds prevail 

 are occupied by conifers. Wind affects the growth and form of trees not only indirectly, 

 by its influence on such site-factors as soil moisture, transpiration, temperature, and expos- 

 ure of foliage to the light, but also directly, by its physical effect on the plant tissues. Inter- 

 nal stresses and friction between the fibres result in eccentric growth, and also help to stunt 

 the tree by interrupting sap-flow and by affecting cell structure and turgescence. Inves- 

 tigations made at Bonn showed clearly that the stunting effect of wind increases rapidly with 

 wind velocity. — W. N. Sparhawk. 



114. Bernberk. Die Wasserversorgung der Pflanzen im Winde. [The supply and main- 

 tenance of water in plants during wind.] Naturwiss. Zeitschr. Forst- u. Landw. 18: 121-141. 

 1920. — The physiological action of the mechanical strength of winds in relation to trans- 

 piration is manifested in an increase in the amount of moisture given off. The rate of this 

 increase is, in general, governed by the conditions of firmness or stability and inflexibility 

 as opposed to the attacking force of the wind. The following are three ways in which the 

 mechanical action of the wind leads to an increase in water loss: (1) The intercellular gas 

 renews itself in spite of reaction of the stomata, whereby an increase in intercellular trans- 

 piration is involved. (2) An excess of pressure in water conducting tissue is occasioned by 

 torsion, pressure, etc. This forces water out of the lumen and membranes of cells subject 

 to the higher pressure into cells under lower pressure, into the intercellular spaces, or 

 through the epidermis into the free atmosphere. This internal pressure in very strong winds 

 can become so great that the cell walls are burst. (3) The water permeability of the outer 

 epidermal wall and the periderm is decreased by deformations. — The quantity of transpiration 

 is strongly influenced by the humidity of the air. Death through excessive water losses and 

 poor conduction reaches its maximum with the lowest relative humidity. Young tender 

 organs are not as unprotected against wind, transpiration, and frost as may be supposed. 

 The younger and the richer the tender-walled cells are in plasma, the more resistant are they 

 to wind pressure. The period of greatest susceptibility is immediately after the period of 

 greatest vegetative activity. The spiral grain in trees much exposed is due to the mechanical 

 action of the wind. The best protection against the mechanical action of wind, ^s illustrated 

 by the palms and grasses, consists in a flexibility, which allows the plant to bend before the 

 wind. — J. Roeser. 



115. Burns, George P. Eccentric growth and the formation of redwood in the main 

 stem of conifers. Vermont Agric. Exp. Sta. Bull. 219. 10 p., 4 pi, 10 fig. 1920.— See Bot. 

 Absts. 7, Entry 318. 



