Johnson — Willow Canker. 155 



an opportunity of asserting itself more fully. One cause of failure 

 is illustrated by Plate XV., fig. 2. The willow is a surface-rooting 

 plant, and in planting, the sets, 12-13 inches long, should be put 

 into the ground in a sloping direction, not upright, as was done in 

 most of the planting at Letterfrack. Roots do not form on the 

 lowest part of the rod if too far into the ground ; the rod then 

 remains much thinner than the rooting, more vigorous upper part. 



The land used for planting at Letterfrack was raw bog. This 

 needs thorough draining and suitable manure. The effects of 

 insufficient attention to these two important points are clearly 

 observable in the beds. Again, the best osier-cultivators insist on 

 the necessity of cleanliness of the ground. Weeds, they say, are 

 fatal to the growth of the sets, and should be rigorously kept 

 under. At Letterfrack the weeds have got the upper hand ; and 

 some of the plots are full of rank grasses and other weeds. At 

 Kockfield I also saw hundreds of bundles of rods stored green for 

 several years past, full of disease, and now, no doubt, spreading 

 contagion. They should have been burnt when first found useless. 



A too wet, poor, peaty soil would distinctly favour the canker 

 disease once in possession of the rods, or would render otherwise 

 healthy ones liable to fall a prey to the attacks of the fungus. The 

 black specks in the canker-spots prove to be of three kinds, dis- 

 tinguishable partly by their contents, partly by their size and 

 shape. The specks are confined to the blisters, and are often 

 found aggregated together, so that three or four of them form one 

 compound common speck, divided into compartments by their 

 cellular walls, raising the host epidermis as they form, and 

 bursting through it as one body (Plate XIV., fig. 1). All the 

 black specks are minute, dark- walled bladders, each with a small 

 opening or pore through which the contents, when ripe, escape into 

 the outer air. 



In one kind the bladder, *76 x -3 mm., is lined throughout its 

 whole inner surface with a layer of short cellular rods, or conidi- 

 ophores, each carrying at its end a single, oblong, fusiform, septate 

 conidium, 8*7 x 2*3 /x (Plate XIII. , fig. 3). The bladder is a 

 pycnidium, and serves, no doubt, by the production of the conidia, 

 for the vegetative propagation of the parent fungus. By means of 

 these conidia, judging from analogy, the fungus reproduces itself 

 throughout the growing season on other parts of the host, or on 



