THE ZALLINGEEIAN PERIOD 31 



vertised and, of course, overestimated, but had the 

 effect of calling more general attention to the economic 

 importance of plant diseases and created a demand for 

 semi-technical works on the subject. Such were immedi- 

 ately forthcoming. Three books of this type appeared 

 in the years 1794 and 1795 alone. 



Perhaps the most important of these is that by 

 Plenck, on the physiology and pathology of plants.' 

 The author attempts to treat the diseases of all cultivated 

 plants of importance at that time. This work is valuable 

 because based apparently on thorough observation. The 

 two others are: Schreger's Introduction to a correct 

 understanding of the diseases of trees^; and Ritter von 

 Ehrenfels' Diseases and injuries of fruit and garden 

 trees.' Both give good descriptions of cankers, especially 

 of the Nectria canker still so destructive in Europe. 

 They attribute most of the ailments of plants to 

 unfavorable soil conditions, climate, or the inherent 

 disposition of the plant to become diseased (Sorauer, 

 1909:48). Writings dominated by the theories and 

 dogmas of this period continued to appear far into the 

 nineteenth century and were numerous during the early 



' Plenck, Joseph Jacob von: Physiologia et pathologia plantarum, 

 pp. 1-192, Veinnae, 1794. (Pages 123-184 only, deal with pathology 

 including insect injuries.) This was translated into Italian by G. 

 Pagani in 1804 under the title: Fisiologia e patologia delle piante. 



^ * Schreger, B. N. G.: Erfahrungsmassige Anweisung zur richtigen 

 Kenntniss der Krankheiten der Wald- und Gartenbaume, der Getreidear- 

 ten, Futterkrauter, Kiichengewachse und Blumen, nebst den bewahrtesten 

 Mitteln dagegen; fiir Forstbediente, Oekonomen und Gartenliebhaber, 

 pp. 1-518, Leipzig, 1795. 



'* Ehrenfels (J. M.), Ritter von: tjber die Krankheiten und Ver- 

 letzungen der Frucht und Gartenbaume, pp. I-XX + 1-232, Breslau, 

 1795. 



