13 



Red Rust : 



ITS NATURE, APPROXIMATE CAUSES, and PROBABLE 



CURE. 



By Otto Teppeb, E.L.S., London ; Corresponding Member. 



(Abridged.) 

 [Bead November 1, 1879.] 



The subject under consideration divides itself naturally into 

 various questions, viz. : — 



"What is Red Red Rust, and bow is it produced ? 



"What laws govern its development, and tbe growth of its 

 fostering plant ? 



Wbat will check tbe one and promote tbe otber ? 



Tbat Red Rust, or mildew, is a fungus, alike witb mould,, 

 smut, brand, &c, bas been proved and known long ago. Tbe 

 reddisb dust, wbicb f urnisbes tbe name, is tbe accumulation of 

 tbe spores or seed germs of tbe fungus, and its appearance 

 denotes tbe last stage of its development and tbe completion 

 tbereof . Tbe first plants upon wbicb it appears (as frequently 

 observed by me) are self-sown plants of black oats, barley, and 

 wbeat, in tbe order tbey are named, tbe first two being seldom 

 and tbe latter not necessarily injured by it ; one reason being 

 tbat this, tbe first stage (for according to Mr. C. Cooke there 

 are three or four) only attacks the older leaves in quite au 

 inconspicuous manner, the few spots being overlooked and 

 assigned to different causes by the practical farmer. Should 

 the sown crop be attacked, the indications will appear in the 

 same order — first by faint minute streaks upon tbe leaves and their 

 sheaths, then on the portion of tbe stalk covered by the latter. 

 These gradually augment, at the same time raising tbe cuticle 

 or outer skin into minute longitudinal ridges and protuber- 

 ances plainly discernible to tbe touch. These increase and 

 finally burst almost spontaneously over vast areas, or only in 

 limited localities, according to local climatal circumstances. 

 Then only, when tbe fact thus forces itself upon the ordinary 

 observer, is it noticed ; but at this stage the mischief is done, 

 and nothing can stay the consequent destruction of the crop. 



"Whence did it come ? How did the destroyer get into tbe 

 plant ? To answer these questions, we must shortly consider 

 tbe growth of fungi and their propagation. 



