218 FUNGOID PESTS OF CULTIVATED PLANTS. 



TREE-ROOT ROT. 

 Armillaria mellea (Fr.). 



The blackish cord-like strands of mycelium long known under the 

 name of Rhizomorpha are for the most part connected with this Agaric, 

 which is common everywhere at the roots of trees. This mycelium con- 

 sists of blackish cord-like strands of the thickness of fine twine, which 

 creep over the roots, and the base of the trunk, close to the ground, 

 radiating on every side until they come in contact with other roots, 

 which are attacked. The rhizomorphs do not enter the roots, but give off 

 delicate branches which enter the roots and form white sheets of mycelium 

 between the bark and wood. 



The complete fungus grows in dense clusters at the foot of trees, and 

 is an Agaric, of the Mushroom form, with a cap two or three inches across, 

 of a honey-yellow colour, generally clad with darker scales. The stem is 

 from three to six inches long, smooth, and rather paler than the cap, 

 darkest at the base. Gills white when young, becoming creamy with 

 age. The stem above the middle is surrounded by a white frill or ring. 

 The spores are white (9 x 6 /u) and are produced in great profusion, falling 

 and settling on the grass and surrounding objects like a dense white 

 powder. 



Care should be taken in orchards not to wound the roots of trees with 

 the spade. All clumps of the Agaric should be destroyed. Affected trees 

 should be isolated by digging a trench around them. 



Sacc. Syll. vi. 289 ; Cooke, Him. No. 32 ; Mass. PL Dis. p. 201, 

 fig. 47 ; Cooke, Hdbk. No. 36, fig. 36 ; Journ. E.H.S. xxvi. 1902, p. 735, 

 fig. 309 ; Marshall Ward, Timbers &c. p. 154, figs. 15, 16. 



POPLAR LEAF- SPOT. 

 Septoria Populi (Desm.), PL XX. fig. 31. 



This common leaf-spot on Poplar leaves occurs on the upper surface, 

 and is characterised by small orbicular spots, which are sometimes con- 

 fluent, whitish or bleached, greyish towards the circumference, with a 

 brown border. The receptacles are few and pale at first, becoming blackish 

 when dry. Sporules rod- shaped, obtuse at the ends, and curved (45 x 3 />),. 

 with a single septum. 



Recorded in France, Belgium, Portugal, Italy, and Siberia. 



Sacc. Syll. iii. 2712 ; Cooke, Hdbk. No. 1317 ; Grevillea, xiv. 101, 

 No. 485. 



POPLAR-LEAF ANTHRACNOSE. 

 Marsonia Populi (Lib.), PI. XX. fig. 32. 



This parasite appears to be the same as that described by Berkeley 

 many years ago under the name of Asteroma labes, and is found on the 

 leaves of Populus nigra, italica, and alba. 



The spots are on the upper surface, and are somewhat rounded, often 

 confluent, brown, with a dark margin, upon which the pustules are 

 scattered. Conidia somewhat pear-shaped (20xl2fi), divided by a trans- 

 verse septum into two cells, expelled when mature in whitish tendrils. 



