DISEASES OF PLANTS. 1153 



A bacterial disease of lettuce, V. L. Stkvk.ns (Xortti Carolina N/r/. h'lit. l!Hn\ 

 pp. 2!), 30, fig. 1). — The author states that in 1007 lettuce phiiits were received 

 in which the leaves were mildly infee^^ed with some disease that was character- 

 ized by the appearance of pale, yellowish-jrreen spots 1 mm. or less in diameter. 

 Later these spots turned straw colored and then brown, and as the spots en- 

 larjred there was considerable shrinkiiifj; and drying of the diseased tissues. 



T'pon microscoitic examination no fungus was found, but the tissues were 

 swanuiug with bacteria. Cultures were made of these organisms, aud although 

 inocrlation experiments did not prove successful, the absence of any other 

 causal agent aud the universal appearance of bacteria in practically pure cul- 

 tures made it seem in-obable that the disease is due to l)acteria. It is thought 

 possible that the disease may be the same as that reported by the Massachu- 

 setts Station ( E. S. K., 1!). p. 24.".). 



Fungus diseases of sweet potatoes (Agr. News [Barbados], 7 (1908), No. 

 I.j2, pp. .56*. 59). — Attention is called to the fact that the black rot of sweet 

 potatoes is due to the fungus Siiltarottrenta flmhriatum, or Ccratocijstis fimhriatu, 

 as was first repoi'ted. 



Further attention is called to the fact that the only fungus disease of sweet 

 potatoes in the West Indies that is of grave importance is caused by a basidio- 

 mycctons fungus, which is probably a si>ecies of Marasmius. The mycelium of 

 this fungus envelops the roots underground and renders them untit for use. 



Notes are given on a number of other diseases of sweet potatoes that occur in 

 different cotuitries but which have not yet been reported from the West Indies. 



Some stem, tumors or knots on apple and quince trees, G. <i. Hedgcock 

 {U. *S'. Dcpt. Agr., Bur. Plant Indus. Circ. 3, pp. 16, figs. 11). — A peculiar form 

 of tumors or knots has been observed on apple and quince trees in different 

 parts of the I'nited States for a number of years and has been under observa- 

 ti(m by the author during the past 5 years. 



The tumors occur on the trunks, limbs, and twigs of apple aud quince trees. 

 On the a])ple tree the disease appears most often on the trunk and larger limbs, 

 but in a number of instances affects the twigs and smaller limbs. 



The tumors, as described from a specimen from the Arkansas Experiment 

 Station, were exceptionally large at the beginning and frequently appeared in 

 the form of a smooth swelling surrounding the base of a dormant bud, quite 

 often the terminal bud of a twig. The tumors vary in size from that of a small 

 pea to others attaining a diameter of 2 to 3 in. During the first period of their 

 growth tile swellings are covered with a thiclv, fleshy layer of meristem and 

 bark tissues. Tlie growth is often, quite rapid for the first year or two, and in 

 about o years the bark covering the tumors l)ecomes ruptured and ceases to 

 grow. As the bark falls away, small elevations, which resemble shoi't thiclc- 

 ened root cajhs, ai»pear on the surface of the tumors, .giving them a warty ap- 

 ]iearance. In the older forms in some cases the tumors show a slight decay. 

 On the quince the disease originates quite similarly to that described for the 

 apple tree, with the exception that tumors have not been noted affecting the 

 ends or bases of small twigs. 



A number of experiments have been conducted to throw light upon this 

 disease, and scions were taken from the specimen tree mentioned above aud 

 grafted on roots from healthy apple seedlings. One hundred of the grafts were 

 planted, and at the end of the season OU per cent were found to be affected with 

 the woolly-knot form of the hairy-root disease. It appears that the hairy-root 

 disease may have at least 3 forms — the simple, the woollj^ knot, and the aerial 

 forms, described above. 



Nurserymen are advised to be careful in the selection of scions and stocks 

 for propagation aud to see that they are always taken from healthy trees. 



