PREVENTIVE AND < oM KATIVF. MKAM'KKS. 7-~> 



needle-rust). The exclusion of the aspen from the neighbour- 

 hood of pine plantations is advisable as a means of limit in- 

 the pine-disease, and is now being recommended in forestry. 



Still another example is Puccini graminis the rust of 

 wheat and its A'nlnin< on the barberry. This is, in all 

 probability, able to reproduce itself by means of uredospores on 

 wild grasses, and to retain its position without the barberry, yet 

 the latter doubtless tends to distribute the disease, and it- 

 removal minimises the risks of attack. 



An investigation of the heteroecious rust-fungi will easily 

 furnish many examples of the same kind, and lead to the con- 

 clusion that Eui>liurl>in cyparissias, for example, should be 

 exterminated near fields of peas or other Leguminosae because 

 of Vroui i/<-< .-> ji/.-</, and U. strittix. 



III. Avoidance or removal of conditions which favour infection. 



Various examples of this have already been given when 

 the conditions disposing plants to disease were under considera- 

 i it in in our last chapter. 



(1) The most important measures of this class are those 

 directed against infection through wounds. This may be 

 attained by avoiding any unnecessary wounding of woody plant-. 

 and the immediate treatment of any wounds rendered necessary 

 in pruning or other operations. 



"When the steins of woody plants are injured, the first step 

 towards healing the wound proceeds from the tree itself. 

 Conifers containing resin have in it a MTV ready agent im- 

 mediately available : the resin escapes from its ducts ami soon 

 harden- into a eiu-t on exposure to air. In the case of nn- 



resilious conifers and of broad-leaved trees, the first step> 

 towards healing are lesfl obvious, but it has been found that a 

 healing tissue immediately begins to form on wounded surface-. 1 

 It Consists of a parenchyma, the formation of which is indin ed 

 apparently by atmo-pheiic air penetrating into the wood, and 



1 v. Tul.ciif, " 1'fln-r iH.rmali- u. patliiiL'i-ii" KiTiiliililuiii; l. H>l/|>ll:e 

 ii. <1. Ili-liaiiclluiiL' v, Wimili'ii lc-i -M-lln n. Zeitachrtfl f. Fortt. u, ./";//. "- . I-- 1 ' 



(!niitaiiM l'>il'liM_'i .ijiliy i.f allinl |ta|irr>. 



I: llMiiir. Disease* of Tree*, l-lni-lisli K.litic.n, Ism. 



Gannersdorfer, >'''./';/>'/. -/. /.-. .ll.n,/. ,/. ll'-'--. n^-lm/t. \'H-IIM.I. l^-i 



llcM-lmi. " Ueber 'li- Fun. 'tic. n <\. \.-L;.-I. Gl . /..iiin.'i, I" 



