140 TWENTY-FIFTH ANNIVERSARY REPORT. 
ing: (1) A case of premature coloration and dropping of pear 
leaves which was ascribed to defective nutrition.?*° 
(2) Trouble with pear trees stored in a nursery cellar.176 The 
upper portions of the trees turned black. Upon investigation it 
was found that the trouble had been brought about by sudden 
thawing of the trees. The sand covering the roots of the trees 
had become frozen, and in order to thaw it quickly a fire had been 
built in the cellar. | 
(3) Body blight.147 Studies on this were made in connection 
with the investigation of apple canker. A full understanding of 
body blight was not obtained, but it was proven that the apple 
canker fungus!*S may attack pear wood and produce lesions similar 
to those found on pear trunks affected with body blight. 
PLUM. 
Of the various plum diseases, leaf spot has received most atten- 
tion. During three years, 1885 to 1887, a considerable study was 
made of the life history of the leaf spot fungus.’2? While not fully 
demonstrated, it was shown to be highly probable that the fungus 
has three different spore forms, one of which is an ascigerous form. 
Strange to say, this matter stands to-day where it was left by the 
Station twenty years ago. The occurrence of an ascigerous form 
in the life cycle of the fungus has been neither proven nor dis- 
proven. 
Experiments on the treatment of leaf spot were begun in 1887, 
when promising results were obtained with potassium sulphide used 
as a spray.’8? In 1891 and 1892 bordeaux mixture and the ammo- 
niacal solution of copper carbonate were tried on nursery stock.}*4 
The latter injured the foliage, but the former gave results sufficiently 
good to warrant further trial. The experiments were continued in 
1893 with bordeaux only.4** This year the beneficial effect of 
spraying was marked. The sprayed trees held their foliage longer 
and made a larger growth of tops and roots. 
™ Rpt. 3:369 (1885). 
** Bul. 200:83-85 (1901); same in Rpt. 20:143-146. 
“7 Bul. 163 (1899); same in Rpt. 18:331-360; Bul. 185 (1900); same in 
Rpt. 19:342-350. 
8 Spheropsis malorum Pk. 
*° Cylindrosporium padi Karst. Rpts. 5:276-281 (1886) ; 6:347 (1887). 
* Rpt. 6:350 (1887). 
*1 Rpt. 11:659-664 (1892). 
® Bul. 72 (1894); same in Rpt. 12:690-693. 
¢ 
