554 Journal of Agricultural Research voi.xv. No. lo 



the cotyledons and the upper part of the stem turning upward away from 

 the soil. The epidermis, while showing no evidence of serious injury 

 beyond the loss of pigment, may suffer microscopic ruptures. On the 

 upper side of a yellow-pine seedling at the point where a lesion was being 

 developed by bending, observation with a hand lens showed that minute 

 drops of liquid were extruded from the epidermis apparently at small rup- 

 tures, which, however, could not be detected after the drops had disap- 

 peared. Stomata may, of course, have been the points of exit of the sap. 



The importance of lesions produced by bending without outright break- 

 age in the seed beds is slight, unless very high winds occur during the first 

 lo days after the appearance of the seedlings. The fact that the lesions, 

 like white-spot lesions due to heat, remain definitely limited for a week 

 or more, together with their lighter color, serves to distinguish them from 

 those caused by the usual damping-off organisms. Positive differentia- 

 tion on the basis of color alone is not entirely safe, three or four days' 

 observation being necessary to determine whether or not a lesion is 

 parasitic. 



It may be mentioned that in older plants a girdling of Russian wild 

 olive, several months old, by a transverse lesion at the soil surface, fol- 

 lowed by death a number of weeks later, and the girdling and local collapse 

 of the soft young shoots of 2- or 3-year-old pine nursery stock, both 

 observed in regions of high wind, may also prove to be due to excessive 



bending. 



DROUTH INJURY 



Death of young seedlings from drouth is undoubtedly sometimes 

 confused with damping-off. Seedlings so young that the stems have not 

 finished elongating may remain erect for some time after being killed 

 either by drouth or normal damping-off, as the compactness of the tissues 

 apparently prevents immediate collapse from water loss, and decay takes 

 place but slowly. When the seedlings are old enough to have stiff, wiry 

 stems, difficulty again arises in distinguishing between seedlings killed by 

 drouth and those killed by the late type of damping-off. Therefore 

 during the first week and after the third week from germination it is not 

 usually possible to distinguish drouth injury from damping-off by the 

 condition of the individual seedling. Fortunately the distribution of the 

 diseased seedlings often gives a clue. Damped-off seedlings, especially 

 in the late damping-off type, are usually so grouped as to definitely indi- 

 cate infection foci. This is not the case in drouth injury. 



At the intermediate age of one to three weeks it is often possible to 

 distinguish between drouth injury and damping-off by the condition of 

 affected seedHngs. At this stage seedlings dying from drouth show 

 prompt and unmistakable wilting, while the damped-off seedling at first 

 remains turgid, typically falling on account of the decay of the base of the 

 stem before wilting of the rest of the stem takes place. Seedlings just 



