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SCIENCE 



[N. S. Vol. XXVIII. No. 709 



fully on fresh and sterilized twigs of apple, 

 rose and pliun. On sterilized twigs the pyc- 

 nidia developed were often strongly flask- 

 shaped, and in many cases hairy. 



Repeated attempts were made to inoculate 

 the fungus on the leaves of young seedling. 

 Yellow Transparent, Ben Davis and York 

 Imperial apple trees in the green-house, with 

 spores taken from pure cultures on various 

 media, and placed on the surfaces of leaves 

 kept moist under bell-jars. Only negative 

 results were obtained from this work, though 

 it was continued for five months, and on leaves 

 of widely differing degrees of age and vigor. 



Inoculations were also attempted on leaf 

 tissue which had been previously injured by 

 various artificial means, scalding, abrasion of 

 the epidermis, and punctures made with both 

 hot and cold needles. Inoculation on scalded 

 tissue was usually successful, and on abraded 

 tissue always. Fruits of the fungus quickly 

 appeared on tissue which had been killed by 

 abrasion and inoculated, but the area of the 

 leaf killed by the abrasion was seldom appre- 

 ciably enlarged by the fungus. Of a number 

 of attempts to inoculate the leaves at punc- 

 tures made with needles, only two were suc- 

 cessful. Hot needles were then used in making 

 the punctures, small areas of leaf tissue being 

 killed by the heat of the needle; the leaves 

 were then sprayed with the atomizer, as in 

 previous work, the spores spread over the sur- 

 faces of the leaves with the platinum loop, 

 and the plant kept moist under a bell-jar. 

 Within three to five days after inoculation a 

 large number of the inoculated spots produced 

 by the hot needle enlarged to three or four 

 times their original diameter, and fruits of 

 Coniothyrium piriim speedily appeared, usu- 

 ally in a ring near the outer edge of the spot. 

 The fungus fruited on almost every such 

 puncture inoculated. Checks were obtained 

 by making a row of the hot needle punctures 

 on each side of the mid-rib of the leaf, but 

 placing spores only on the row on the right- 

 hand side. A very few of the check spots on 

 the left-hand side were evidently inoculated 

 by spores accidentally washed over from the 

 other side in watering. The rest of the check 

 spots did not develop fungous fruits, and did 



not spread beyond the limits of the area orig- 

 inally killed by the heat. Punctures were 

 sometimes made with a cold needle at the 

 same time and on the same leaves as success- 

 ful inoculations at hot needle punctures, but 

 at only two such punctures were spots ever 

 produced by the fungus. 



These results of inoculation make it seem 

 that Coniothyrium pirina is a facultative or 

 wound parasite only, able to produce spots on 

 apple leaves provided it has a little killed or 

 injured tissue in which to get a start. That 

 it causes a considerable amount of leaf-spot 

 under orchard conditions is quite possible, but 

 not as yet demonstrated. 



An inoculation was also made on the living 

 twig of a seedling apple tree in the green- 

 house by making an incision in the bark and 

 inserting with platinum loop a drop of water 

 containing spores from a pure culture of 

 Coniothyrium pirina. The wound was then 

 wrapped with absorbent cotton, and kept moist 

 for a number of days. Forty days later sev- 

 eral excellent fruits of the Coniothyrium were 

 found breaking through the bark at the very 

 edge of the area injured by the incision. 

 There was no further development of the fun- 

 gus, nor was there any injurious effect noticed 

 on the health of the shoot above the point of 

 inoculation. This seems to confirm the state- 

 ment that Coniothyrium pirina is a faculta- 

 tive parasite only. A number of subsequent 

 attempts were made to inoculate the fungus 

 on living apple stocks kept moist under bell- 

 jars but not wrapped with cotton; these were 

 uniformly unsuccessful. The trees on which 

 these inoculations were made were nearly aU 

 growing vigorously at the time of inoculation. 



The readiness with which the fungus grew 

 on dead twigs in the laboratory suggested that 

 it could probably be found on dead twigs in 

 nature. On May 15, 1907, a fungus morpho- 

 logically identical with Coniothyrium pirina 

 was found at Cassville, W. Va., on dead twigs 

 of a quince bush, the leaves of which were 

 known to have borne many spots containing 

 the fungus two years previously. Pure cul- 

 tures were easily obtained from these twigs by 

 plating, and spores taken from one of these 

 cultures were used successfully in producing 



