094 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



shine and the air is very dry. From the pulp of crushed frozen Potatos 

 a poisonous alkaloid is extracted. 



Noel Bernard, after studying the Orchid family, attributes the formation 

 of tubers on the stolons of the Potato to the presence of a fungus of 

 the genus Fasarium. Owing to the presence of this organism the tubers 

 are formed earlier, more regularly, and closer to the stem, and do not 

 appear at the extremity of the long running stolons which one sees in 

 most plants. Placing farmyard manure in immediate contact with the 

 seed Potato is very favourable to the spread of the fungus and infection of 

 the root ; in fact the manure itself often contains this fungus, and if germs 

 of the fungus already exist on the seed Potato, the farmyard manure 

 contributes to its development. 



The practice recommended by Aime Gerard, of choosing Potato seed 

 from the plants which have produced the largest yield, has given excellent 

 results. It is because these tubers come from strong buds borne by a 

 parent plant richly infested with this fungus, and by which they are more 

 capable of transmitting the fungus to their descendants. — C. H. H. 



Potatos, Formation of Thread-sprouts in. By M. G. Delacroix. 

 {Comp. Bend. December, 1900, p. 1006). — The term thread-sprouts is used 

 in the case where the sprouts of Potatos grow considerably in length but 

 remain slender. 



When planted such tubers produce badly developed tufts, and often 

 not a single shoot appears above ground, or if such do come through the 

 soil they are morbid and rapidly shrivel and die. 



Some varieties when planted in rich soil produce a crop, but the pro- 

 duct of such diseased tubers always presents the characters of the disease. 



When Potatos are dug up in the autumn those tubers which will 

 produce the disease cannot be detected with certainty, and it is only 

 towards the end of winter that the presence of thread-like sprouts 

 indicates with certainty their nature. At this stage such tubers are often 

 harder in substance than normal ones, and microscopic examination 

 often reveals the presence of various organisms, Bacillus solanicola, 

 B. caulivorus, Fusarium Solani, &c. None of these are, however, the 

 cause of the disease. Neither can thread-sprouts be attributed to dryness 

 of the soil. 



The true cause of the disease is to be attributed to degeneration and 

 lowered vitality, presented by so many varieties of Potatos, which is 

 entirely due to the universal practice of vegetative reproduction: that is, 

 continuously raising a crop from tubers instead of sometimes from seed. 



Under such conditions a certain set of characters become hereditary, 

 and the plants lose to a great extent the very important character of 

 adaptability. As a consequence such tubers cannot resist the attacks of 

 various fungi, bacteria, &c, which are successfully resisted by normal 

 Potatos. Again, under the conditions stated, the tubers may become 

 incapable of elaborating the necessary diastases or ferments for the 

 solution of the substances required as food for new growths or sprouts, 

 hence emaciated thread-sprouts are formed. 



If Potatos are allowed to "sprout" in the light before planting, 

 diseased tubers can be rejected; this method, however, is only a temporary 



