765 



give a cork-like appearance. They cannot respond any longer to the swelling 

 of the fruit, which, therefore, cracks. The w^oiind cork formed in the 

 cracks, together with the tissue killed by the Bordeaux mixture, then causes 

 the peculiar "rust figures" shown in Fig. 169. The amount of injury 

 increases with the tenderness of the skin, which shows the initial stages of 

 browning, as a rule, around a hair or a stoma. With the increasing age of 

 the fruit, the hairs are thrown ofif normally and lenticels are produced instead 

 of stomata. In this the wax 

 coating is thickened and the 

 fruit becomes immune to the 

 poisonous copper. Brown spots 

 may be produced also on the 

 leaves which at times repture 

 (Fig. 172). Naturally the 

 blossoms suffer most severely. 

 It can be assumed with cer- 

 tainty that in these blossoms 

 the copper unites with the cell 

 contents. Hedrick's remark 

 that a considerable addition of 

 lime scarcely decreases the 

 injury is worthy of consider- 

 ation in regard to the prepa- 

 ration of the Bordeaux mix- 

 ture. This is treated more 

 thoroughly in the second vol- 

 ume of this book (page 521). 

 All that is true of calcium 

 copper mixtures holds good to 

 a higher degree in the Asur'me 

 in which ammonia is used to 

 neutralize the copper vitriol. 

 Pure deep blue solutions are 

 produced, according to the 

 amounts of ammonia used, 

 such as "Bouille Celeste" and 

 the "Azurine Siegwart," or 



especially with greater dilution basic copper compounds remain as a precipi- 

 tate, as is found in the " Crystal- Asurine Mylius." The more ammonia used, 

 the greater is the danger of burning the leaves\ 



Anaesthetica. 



In considering the so-called "forcing zv'ith ether," that is to say the 



process, of exposing the plants to ether vapor in order to hasten their growth, 



1 Kulisch, p., tJber die Verwendung- der "Azuiine" zur Bekampfung' der 

 Peronospora. Landwirtsch. Z. f. ELsass- Lothringen 1907, No. 26. 



P"ig-. 172. Apple leaf with dead spots and holes 



in the tissue, after spraying- with Bordeaux 



mixtiu-e. (After Hedrick.) 



