CRONAKTIUM 



317 



' Teleutospores. Columns hypophyllous, cylindrical, curved, 

 up to 2 mm. long, crowded especially along the veins of the 

 leaf, sometimes covering the whole leaf, orange to brownish- 

 yellow ; spores oblong, smooth, reaching 70 fi long x 21 fi broad. 



vEcidia on stems and branches of Pinus Cembra, P. monti- 

 cola, P. Strobus, March— June ; uredo- and teleutospores on 

 Uibes nii/rum, R. rubrum, etc., July — October. Uncommon 

 except when imported; Surrey, King's Lynn, Exeter, West- 

 burv, Woburn, Windsor Forest, Perth, etc. (Fig. 240.) 



Fig. 240. G. ribicola. a, spore of Peridermium Strobi; b, the teleutospore- 

 columns on leaf of Eed Currant (reduced); c, uredospore; d, top of a 

 column of teleutospores, x 600. 



This dangerous parasite, sometimes called the Weymouth Pine Rust, 

 is confined in its secidial stage to the five-leaved Pines ; it is reported on 

 the continent also on P. excelsa and P. Lambertiana. The aecidiospore is 

 distinguished from that of Peridermium Pini and P. Cornui by the fact 

 that a great part of the surface is smooth. The attacked trees are 

 stunted, the tops show a bushy growth that can easily be recognised; 

 the part where the mycelium is growing is swollen. In the Currant, the 

 attacked leaves become thicker in texture, and different in colour. 



It was first discovered, in this country, at King's Lynn by Dr Plow- 

 right, who found the Gronartium on leaves of black, white, and red 

 currant on July 3, 1892. On August 13 he exhibited in London a branch 

 of P. Strobus affected by the mycelium of the alternate stage; the tree 

 grew about fifteen yards away from the currant bushes. On March 19, 

 1893, he found the Peridermium in full perfection at the same place. 



Though the secidium occurs in Europe chiefly on the Weymouth Pine 

 (/'. Strobus), yet that cannot be its original host, since neither Cronart'm m 

 ribicola nor Peridermium Strobi was found in America (the home of 

 P. Strobus) until the fungus was imported on it from Germany. P. Cembra, 



