DISEASES OF PLANTS. 343 



plMiits and has l)r('ii ohscrNi'il on niaii\- spcciinciis ol" i^iiisciii; submitted for 

 examination. 



The author reconnnends tlio destruction of all dead jilants. sjtra.vin.i,' with 

 Bordeaux nuxturi-. and fre(iu(Mit chanjrinj;- of location as far as i)Ossil)le or 

 sterilization of soil. In sprayinir, particular attention must be paid to covering 

 the petioles and stem in the re^'ion of the fork, as this seems to be the jwrtion of 

 the plant most subject to attack. 



Diseases of beets and mangels, G. Masses {Roy. Bot. Ganl. Kcir, Bui. Misc. 

 hi form., J HOG, Xo. 3, pp. .'/'J-dO, fi(/.s. 5). — Notes are given on a number of dis- 

 eases to which beets and mangels are subject, among them beet cank<>r. beet 

 rust, leaf spot, mildew, root rot, beet-root tumor, white rust, scab, heart rot, 

 etc. Among the diseases described which are relatively little known in this 

 country are the beet canker, due to Pionnotes hetcc, aud the heart rot, caused 

 by tSpha'rella tabiftca. 



The canker attacks beets and mangels in storage, particularly if the roots 

 have inidergone a period of sweating. The fungus causes dingy yellow spots 

 tliat api)ear on the surface of the roots. These soon spread, fonning irregular 

 nodular gelatinous crusts, involving more or less of the root, initil the whole 

 is disorganized and destroyed. The fungus also attacks potatoes, as the author 

 has proved by ninnerous inoculation experiments, and he believes it is identical 

 with that which has been described as P. rhizopliihi, which is said to attack 

 potatoes and dahlias. The author suggests care in storing, so that the roots 

 should be thoroughly dry. and that every precaution should be taken to prevent 

 sweating in storage. 



The heart rot, which has been reported as destructive in some localities, 

 usually manifests itself in August, when the roots have attained a fairly large 

 size. The first indication of its presence is seen in the drooping of the large 

 outside lejives. The appearance is somewhat sinnlar to that of wilting due to 

 lack of moisture, but the leaves do not regain their upright position during the 

 night, and an examination shows a considerable iwrtion of the upper surface 

 of the leaf stalks bleached and studded with nunute black points. The fungus 

 grows downward, entering the crown of the root, which is eventually killed. 

 In this destruction the fungus is frequently aided by other fungi, bacteria, 

 nematodes, etc. When symptoms of this disease appear, all affected roots 

 should be pulled and burned or deeply buried. 



Perpetuation of potato rot and leaf curl, G. Massee {Roy. Bot. Gard. Keic, 

 Bui. Misc. Inform., 1906, JSo. '/, pp. Ill, 112). — A description is given of experi- 

 ments to show the means by which the potato rot (Plnjtophthora infestuns) and 

 the leaf curl (Macrosporium sohini) are perpetuated. Attention is called to tlie 

 freijuent suddeii apjiearance of these diseases and the fact that fields are often 

 destroyed within 124 hours. This widespread destruction has led to an investiga- 

 tion of means of dissemination other than by si)ores to acccmnt ftn* this epidemic 

 form of disease. 



The author took a number of diseased tubers, cut them in halves, and planted 

 them in pots, placing the pots under conditions where the temperature, atmos- 

 I)here, and soil moisture could be controlled. The plants grown in cool, well- 

 lighted, dry bouses showed no trace of disease at the end of 2 months, but when 

 one of the i)lants was removed to a warm house and placed under a bell .jar it 

 was l)Iackened and killed b.v the fungus within 9 days. Similarly marked i-esults 

 were olttained by using potato tubers infested with the Maci'osi)orium. showing 

 tliat this fungus can also be perpetuated by hybernating mycelium present in the 

 tul)ers. 



The experiments seem to indicate that the fungus may be present, but held in 



