80 




















1 seeds of a variety of Barley extremely susceptible to yellow rust 1 
‘i sterilized soil, and properly protected from external infection, yet eve 
then a certain proportion became rusted. He therefore concludes tha 
the fungus arose from “ internal germs inherited from the parent plant, 
which can only be detected just before the eruption of the you 
pustules. Hence, the fungus lives for a long time a latent symbioti 
‘life as a mycoplasma _ in the cells of the embryo, and only assumes th 
visible form of mycelium just before the eruption of the sori. ‘There 
fore the severity of an attack of rust (or mildew) depends: (1) On 
the external surroundings, the environment of the plant, the weather, — 
the soil, manuring, &c. ; if these conditions be favourable, the latent — 
mycoplasm ceases its symbiotic existence and develops into mycelium 
and spores. (2) On the accession of external infective material, 1.@, | 
spores from without. ‘The mycoplasmic symbiosis of P. glumarum 1s — 
more energetic in such varieties as Horsford’s Pearl, which is especially 
liable to this rust than in Squarehead, which is practically exempt, be- 
cause the symbiotic existence of the parasite with this variety is so 
languid as to be practically non-existent. 


Table of Eriksson’s Spore-forms of the Puccinia of the Cereals. 


Puccinia graminis P. 1 Secalis On Rye, Barley 
(Ec. berberidis) Twitch, &c. @ 
2 Avene on Oat, Avena sp. 
Dactylis, Alo- 
pecurus, &c. 
@ IE cities on Wheat. 
4 Aire on A. czspitosa. 
5 Agrostidis on A. vulgaris, &c. 
6 Pow on P. compressa,&c 
P. Phlei-pratensis E. - - - on P. pratense, Fes- 
& H. tuca elatior. 
P. glumarum Sch, 1: Dates on Wheat 
2 Secalis on Rye. 
3 Hordei on Barley. 
4 Elymi on E. arenarius. 
5 Agropyri on ‘Triticum repens. 
P. dispersa E. & H. 1 Secalis on Rye. 
(Ec. Anchusz) 2 Tritici on Wheat. 
3 Agropyri on ‘T. repens. 
4 Bromi on B. arvensis, &c. 

