DISEASES OF PLANTS. 249 



of a parasite. The disease seems always to develop within the flesh of the apple 

 and to extend outward toward the skin, and in many specimens received no 

 trace of the disease was noticed until the fruit was cut open, when the charac- 

 teristic hrown spots were easily identified. 



In the author's opinion, the disease Is due to some obscure pliysloloj^ical caiises, 

 and, as the cells of the affected area are always full of starch, either the patho- 

 logical condition tends to affect the formation of the starch, or, more probably, 

 lh(> action of diastase is locally inhibited. 



The leaf-spot fungus of apple and other fruit trees, .T: L. Sheldon {Torryea, 

 7 (1907). \<). 7, i>i). V,2, lJtS).—ln a publication of the Virginia Station (E. S. R.. 

 4. p. 3.'>4) the brown spot disease of apple was doubtfully attributed to the 

 fungus I'hyUosticta pirina. This same fungus has since been found to occur 

 on the leaves of pear, quince, apple, and plum, causing a disease variously 

 known as l)rown spot, leaf spot, frog eye, etc. 



The author has made an examination of a considerable number of specimens 

 of the fungus and finds that the spore characters do not agree with those 

 originally described for the above species. From the color and other charac- 

 ters he believes it advisable to transfer the fungus from the genus Phyllosticta 

 to the genus Coniothyrium, and the name ConiothytHuni pirina is proposed. 



Die back of peach trees, F. M. Rolfs (Science, n. ser., 26 (1907), No. 655, 

 pp. S7-S9). — -The author notes the occurrence at the Missouri State Fruit Ex- 

 periment Station of the die back of peach trees, due to VaJsa leucostoma, a 

 fungus that has been previously reported as seriously attacking cherry trees 

 in Germany and elsewhere. 



The investigations carried on at the Missouri Fruit Station indicate that the 

 fungus is an active parasite, attacking the twigs, limbs, and trunk of peadh, 

 plum, apricot, and cherry trees. On the peach infection occurs through the 

 buds and wounds at any time during the growing season, but its development 

 is most noticeable during the spring months. Alternate freezing and warm 

 periods during the winter favor the growth of the organism, and it often makes 

 considerable advancement during the warm weather in the winter, the young 

 shoots being frequently killed back from 2 to 15 in. Twigs killed during 

 the winter months at first have a dark purplish color, but later the epidermis 

 and infected areas become leathery and change to scarlet or purple, and finally 

 to a drab color. The diseased portion of the twig soon becomes constricted, 

 making a sharp division between the dead and living tissue, and at this point 

 giun pockets are formed, which usually produce a copious gum flow. During 

 the spring and summer the foliage of the infected twigs frequently wilts sud- 

 denly and takes on a blighted appearance, due to the girdling of the stems. 



Infections on the older branches during the winter and early spring produce 

 oblong wounds and the epidermis covering such wounds cracks and falls away. 

 A callus soon forms on the edge of the injury and finally covers the exposed 

 tissue, but does not unite. On the larger limbs and trunk, especially on the 

 southwest side of the tree, large cankers or sun-scald wounds are formed. 



On the infected areas of the limbs and trunk Cytospora rnhescens and Valsa 

 leucostoma usually develop. Inoculations made with pui'e cultures of V. leu- 

 costoma produced wounds on which C. rubescens invariably developed, and 

 inoculations with pure cultures of Cytospora on peach and plum trees resulted 

 in a constant development of that fungus. 



From his experiments the author believes it safe to conclude that C rubescens 

 is the pycnidial form of V. leucostoma. The pustules of the two forms are 

 constantly Intermingled and resemble each other so closely that it is impossible 

 to distinguish them without the aid of a microscope. 



