Pethybridge — On the Rotting of Potato Tubers. 557 



iustructum. Hypbss oonidiophoree plerumque parum ramosse. Conidia 

 primo acrogena dein etiam pleurogeaa, ovata, apice papillata, zoosporipara. 

 Antlieridia et oogonia in singulis ramis brevibus ex eadem bypba simul 

 orientia. Antberidia oogoniis lateraliter penetrata. Oosporse globosas 

 episporio subtenui, levi, brunneo tectffi. 



Tbe new genus will, fcberefore, contain tbe following species : — Nozemia 

 Cactorum (Lab. et Cobn), N.Fagi{^'Avt.), and'iV. Syringae (Kleb.), N. Nicotianae 

 (,de Haan), and probably otbers, and will remain in tbe family Perono- 

 sporacete. 



Witb regard to tlie other species usually placed in tbe genus 

 Phytophtbora, tbe development of wbose sexual organs is unknown, tbeir 

 logical position would, of course, be for tlie present among tbe Fungi 

 Imperfecti ; but it will probably be found more convenient to place tliem 

 provisionally in one or otber of tbe genera Pbytoplithora or Nozemia, 

 according as tlieir ascertained cliaracters seem to approximate more closely 

 to tbe one or to tbe otber. 



Yll. Pkactical Ognsiderations. 



Pink Eot is a disease wbicb may safely be said to be prevalent in tbe west 

 of Ireland, and present to some extent in otber parts. It is, however, very 

 difficult to estimate, witb any approach to accuracy, what may be the actual 

 losses due to this disease, for it is not yet recognized as a disease sui generis by 

 the farmer ; and any rot wbicli may occur in tbe tubers is, as a rule, but in 

 many cases wrongly, put down to tlie ordinary blight caused by P. iiifestans. 



Although a good deal still remains to be ascertained as to tbe exact way 

 in which the tubers contract tbe disease, and as to wbetlier otber parts of 

 tbe plant may also be subject to attack, yet tbe observations made at 

 Clifden during tbe past four seasons clearly point to tbe conclusion that 

 infection takes place from tbe soil; and also that tbe more» often potatoes are 

 grown in succession in the same soil tbe more severe tbe attack becomes. It 

 seems probable that tbe oospores of the fungus are formed on or from some 

 of the underground parts of tbe potato, remain in the soil as resting spores 

 over winter, and infect the next season's crop. 



On a piece of land which bad been out of cultivation and in grass for 

 several years, but which was planted witb Potatoes in 1912 in some twenty- 

 five separate plots, each of one square perch, the quantity of tubers suffering 

 from Pink Rot in each plot was so small as not to be worth reckoning when 

 weighing tbe crop, and in several of tbem there was not a single afEected 

 tuber. In these plots, wbicb were primarily laid down for spraying 

 experiments against bliglit, tbe quantity of tubers afEected witb blight 



