477 



precaution can be best taken against the various injuries due to wind by 

 means of a protective plantation, suited to the conditions. 



W'e now come to wind-caused injuries to the leaf. The fact that leaves 

 become slit or remain hanging, dried and sear, on the branches in places 

 where wind frequently increases to a storm, is so frequent an observation, 

 especially in coast regions, that it need not be taken up thoroughly here. 

 Just as little need the injuries be touched upon here which are produced in 

 unfolding leaves, by the rubbing of the leaf edges'^. Places thus rubbed 

 through are found with great frequency in horse-chestnut and beech leaves, 

 which, still folded, break from the bud. Young branches are also injured 

 by rubbing, as may be observed in the young shoots of pears and weeping 

 willows (Salix babylonica) after stormy days in summer. Here belongs, 

 further, the whipping of hop vines, whereby the catkins at times become 

 prematurely ripe and red-. The dried edges of the leaf are more important, 

 and as yet but little observed. Since many causes may lead to blighted 

 edges, one must distinguish whether the dried and discolored edge forms a 

 connected outline or one interrupted in places, or whether dry. discolored 

 places push further into the leaf surface from the dead part of the edge 

 (frequently wedge-shaped between the main ribs). 



Only the dr\% browning or blackening outline may be considered as a 

 simple wind injury, as Hansen determined experimentally". This investi- 

 gator constructed* an original apparatus for producing wind in order to 

 eliminate secondary factors (light, excessive heat, drought) which co-operate 

 in the injuries due to wind, occurring out of doors. 



From these experiments, he found, first of all, that /'a^'jr/'ni/ currents in 

 the air dry the tissues most. A simple striking of the wind against a plant 

 growing against a firm wall is frequently less injurious and, under certain 

 circumstances, actually without effect because the wall throws back the 

 wind current. 



In the experiments carried out with this apparatus, a wind continuing 

 day and night, lying between i and 2 of the Beaufort scale, was used. All 

 the individual leaves of tobacco plants, standing in pots, after 24 hours had 

 slight brownings of the edges, while the remaining part of the leaf blade was 

 perfectly healthy and showed no trace of wilting. On an average, the 

 mature leaves suffered sooner than the immature ones. The drying of the 

 tissue always began near the thinnest peripheral veins. The mesophyll col- 

 lapsed, did not contain air but rather appeared translucent, "as if injected." 

 The cell content was deformed, the chlorophyll grains could not be clearly 

 recognized. In many cells, the protoplasm contained slightly brownish 

 granules; the \ascular bundles had turned brown; the boundary between 



1 Caspary, Bot. Zeit. 1869, Sp. 201. — Magnus, Verh. cl. Bot. Ver. f. d. Prov. 

 Brandenburg. XVIII, p. 9. 



- Beobachtung-en iiber die Kultur des Hopfens. 1880. Herausgeg. v. Deutsch. 

 Hopfenbauverein. 



3 Hansen, A., Experimentelle Untersuchungen iiber die Beschadigung der 

 Blatter durch Wind. Flora oder Allgem. Bot. Zeit. 1904, Vol. 9.3, Part I. 



4 Ber. d. Deutsch. Bot, Ges. 1904, Vol. XXII, Part VII, p. 371. 



