LARCH AND SPRUCE FIR CANKER. 33 



secondary cortex. Wounds caused by insects and by hail, and 

 by the breaking of the branches by snow and ice, also expose 

 the cambium to the fungus spores." 



The ascophore or cup of the fungus in D. resinaria is some- 

 what smaller than in D. calycina, more distinctly stalked, and 

 with a yellow or pale orange, nor oiange-red disc : externally 

 white or tinged grey, minutely velvety under a pocket-lens. 

 Conidial form minute, dull orange. (Fig. 4, PL I.) The 

 essential specific characters of the present species are the very 

 minute, subglobose si)ores. averaging 3 x 2-2 '5 jj.; conidia 

 elliptic-oblong, 2x1^. 



Both ascophores and conidia germinate freely when placed in 

 contact with a thin section of cortex or wood of the host-plant 

 in a hanging drop. 



Successful inoculations, i-esulting in the production of ascophores, 

 have resulted from introducing a fragment of mycelium enclosed 

 in resin into punctures in larch and spruce. Ascophores also 

 followed the placing of ascospores in the minute cavity occupied 

 by Chermes laricis on Larix sihlrica, Ledeb. 



Jn addition %o Dasyscypha calycina and D. resinaria, certain 

 other species belonging to the same genus, and bearing a close 

 superficial resemblance to D. calycina, occur on various conifers ; 

 and judging from the appearance of the wound produced, may 

 be considered as wound-parasites. 



Dasyscypha subtilissima, Cooke, has been observed on Abies 

 pectinata, D.C., and Larix europcea, D.C., in Britain, France, 

 Germany, and the United States. 



Dasyscypha calyciformis, Rehm, has been shown by Wagner (7) 

 to be parasitic on Pinus sylvestris, L., Abies pectinata, D.C., and 

 Picea excelsa, Link, in Germany. 



Probably the North American Dasyscypha Agassizii, Sacc. 

 growing on Abies sp. should be included hei-e. 



Summary. 



The larch is most susceptible to canker when quite young, and 

 as the fungus spores in the majority of instances gain an entrance 

 to the living tissues through injuries caused by the larch aphis, 

 Chermes laricis, Hedwig, it follows that seedlings and young 

 trees should be protected against this pest. This can be accom- 

 plished by spraying in the spring with paraffin emulsion, pre- 

 pared as follows : — Dissolve half a pound of soft soap in two 



VOL. XVII. PART I. C 



