BROWN ROT OF SOLANACEAE. 215 



any pathogenic properties, which is quite probable, or else had lost them by cultivation. 

 Nothing Delacroix afterward published on this disease served to clear up the question.* 



In 1902 Gueraud de Laharpe published a note on a French potato-disease said to be due 

 to Bacillus solanincola. He makes the following observations on the subject: 



For several years the culture of the potato in France has decreased more and more, so that now in 

 some departments it is insignificant or has been entirely abandoned, owing to the extremely difficult 

 conditions. The year 1901 was particularly disastrous. 



The Central and Western departments suffered most. Within a few days 

 toward the close of July whole fields were destroyed, leaving of the crop only faded 

 leaves and blasted stalks, while the tubers, when formed at all, were no larger than 

 walnuts. 



The disease appears in general about July 15 upon Jaune de Holland, an early 

 variety, and a little later on late varieties, such as Richter's Imperator. The 

 early varieties suffer most. It is encountered especially in soils which have borne 

 potatoes repeatedly, but it is also found on newly cleared forest or vineyard soil, 

 even on soils which have not borne potatoes within the memory of man. Though it 

 seems to prefer calcareous soil, it causes much injury also in clayey and sandy 

 regions. 



'HI 



Xoomm 



Tyloses are said to be formed in the stems. Delacroix advises soaking 

 sound seed-tubers for an hour and a half in 1 part of commercial formalin diluted with 

 20 parts of water. Delacroix's most susceptible varieties are 40-day Halle and Long 

 Yellow Holland. 



THE ITALIAN DISEASE. 



In south Italy, according to Comes, a disease of tomatoes due to his Bacterium gummis 

 is common. The stems rot usually from the base and the tissues are filled with bacteria. 

 Bad. gummis is now regarded as insufficiently described and it is not known to what the 

 name was applied, as the organism is said to occur in a variety of plants. This is probably a 

 disease of late spring, summer, and autumn. The writer searched in vain for it in the 

 market-gardens about Naples in the early spring of 1906. A great many fields of potatoes 

 were seen, but there was no trace of this disease. Voglino has also reported a disease from 

 Turin, which he ascribes to Bad. solanacearum. 



THE GERMAN RING DISEASE. 



Appel and Kreitz describe a ring-disease, which possibly is caused by Bacterium solana- 

 cearum. the most striking characteristic being a browning or blackening of the vascular 

 bundles. In severe attacks the potatoes do not come up. On the seed-tuber small tubers 

 appear and a great development of shoots, but these are too weak to break the ground and 

 gradually die. When less severe the shoots come up, but are stunted. On subterranean 

 parts are brown cracks which soon become glossy, black spots appear on the leaves, and the 

 plant dies. In the lightest form the affected plants can not be distinguished from sound 

 ones until harvest. Then the leaves wilt and usually show black spots. Such plants 



*Fortunately, Delacroix left an abundance of material both dry and in alcohol to illustrate his potato disease. 

 This, through the courtesy of Etienne Foex, the present director of the Station of Vegetable Pathology, in Paris, the 

 writer had opportunity to examine critically in the autumn of 1913, i. e., since the above text was written. Numerous 

 microscopic examinations were made, but no bacteria were seen either plugging vessels or corroding tissues and cer- 

 tainly nowhere any in numbers sufficient to account for the disease. All of the plants were examined, and each in 

 several places. In the stems and roots of those in alcohol (a large jar of material), nothing was found; but on the 

 shriveled leaves there was a great abundance of Phytophthora infestans. On the dried material evidently collected at 

 another time and place, there was no Phytophthora, but Alternaria solani was found on the brown shriveled leaves, 

 or at least an Alternaria resembling it; and in the xylem vessels in the basal part of some of the stems, a fungus 

 suggesting Fusarium, i. e, a delicate colorless mycelium abstricting colorless elliptical conidia in small numbers. 

 Whatever Delacroix may have first identified as " Brunissure de la pomme de terre," due to his Bacillus solanincola , 

 the museum material which he selected to illustrate it represents only fungous diseases of the potato. 



tFiG. 114a. Margin of a hanging drop showing Bacillus solanincola Delacroix. From an agar culture given 

 to Jones by Delacroix in August 1904. 



