INJURIES INDUCED BY PLANTS 



leaf-scar on the long pulvinus, where they present a bud-like 

 appearance (Fig. 82, b). It also frequently happens that black 

 pycnidia develop on the few dead leaves that have adhered 

 to the shoot (Fig. 82, a). a 



These pycnidia, which are 

 uni- or multicellular, pro- 

 duce numerous small go- 

 nidia (stylospores) at the 

 apex of subulate sterig- 

 mata which spring from 

 the inner wall. These 

 stylospores, which are bi- 

 cellular, colourless, spindle- 

 shaped, and some 13 15 

 micromillimeters in size 

 (Fig. 82, r), appear as white 

 tendrils on the pycnidia in 

 the month of May, at which 

 time they produce the dis- 

 ease, if borne by the wind or 

 rain to the still tender and 

 non-cuticularized shoots of 

 the spruce. 



On May 6th, when growth 

 was active, I infected young 

 spruces by taking a drop 

 of water, in which stylo- 

 spores were suspended, and 

 placing it by means of for- 

 ceps amongst the leaves in 

 the middle of a shoot and 

 partly amongst the bud- 

 scales at its base. Infection 

 succeeded in every case, 

 and eight days later death 

 appeared amongst leaves at 

 the infected points, and 

 soon spread in all direc- 

 tions. On the 1 3th of May, 



FIG. 82. a, a spruce-leader of which the 

 youngest shoot, the apex of the older 

 shoot, and the two lateral branches have 

 been killed, b, pycnidia projecting from 

 the cortex and leaf-scars, magnified five 

 times, c, formation of spores in the inte- 

 rior of a pycnidium, magnified by 400. d, 

 spores germinating in water. e, spores 

 germinating in nutritive gelatine. 



L 



