APPENDIX. 



ON THE NATURE AND PREVENTION OF THE POTATO DISEASE. 



AFTER the preceding pages were in print, I received from Baron Liebig 3 copy 

 of the Journal of the Agricultural Association of the Grand Duchy of Hesse, 

 (Darmstadt,) No* 7, dated 15th February, 1848, containing the account of a 

 method proposed by Dr. Klotzsch (Keeper of the Royal Herbarium, Berlin, and 

 a distinguished Botanist and Vegetable Physiologist,) for preventing the ravages of 

 the potato disease. The proposal of Dr. Klotzsch, and his views as to the nature 

 of the disease, are such as materially to strengthen the opinions expressed on this 

 subject by Baron Liebig, (see pp. 87, seq.) As a knowledge of the method 

 suggested by Dr. Klotzsch is likely to be interesting to many of the readers of 

 this work, I have thought it right to give it in an Appendix. 



WILLIAM GREGORY. 



METHOD PROPOSED BY DR. KLOTZSCH, FOR THE PROTECTION OF THE 

 POTATO PLANT AGAINST DISEASES 



The potato, which is an annual plant, represents, in the tubers developed from the 

 stem, the perennial part of a plant. For while the duration of its development is 

 analogous to that of annuals, its functions coincide exactly with those of dicotyle- 

 donous shrubs and trees. 



" The potato plant differs from all those plants which are cultivated for economical 

 purposes in Europe, and can only be compared to those orchideous plants which 

 yield salep, and which are not yet cultivated among us. 



" The tubers, both of the potato and of the salep plants, are nutritious, and agree 

 in this, that in the cells of the tubers, grains of starch, with more or less azotized 

 mucilage, are collected, while the cell walls possess the remarkable property of 

 swelling up into a jelly, and thus becoming easily digestible, when boiled with 

 water. 



" But while the tuber of salep contains only one bud, or germ, the potato usually 

 develops several, often many, germs. 



" The potato plant, like all annuals, exerts its chief efforts in developing flowers 

 and fruit. Like all annuals, too, it has the power of shortening this period of 

 development, when the power of the roots is limited ; as also of lengthening it 

 when the extent and power of the roots are increased. 



We observe in nature that plants with feebly developed roots often have a weak, 

 sickly aspect, but yet come to maturity in flower and fruit sooner than stronger 

 individuals, well furnished with roots. 



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