46 EXPERIMENT STATION RECORD. [Vol.43 



leaves wore Unuu\ in sovcral lociilillcs which are indicated. In four cases stem 

 rust was found on wheat, in every casf' closely associated with rusted barberry. 

 Studies in the jdiysiolojiy of parasitism. — V, Infection by Colletotrichiim 

 lindeinuthianuni, V. K. Dky {Ann. Bot. [London^, 33 {1919), No. 131, pp. 305- 

 312. 1)1. /». 'IMus is a continuation of the sei-ies iireviously noted (E. S. K., 39, 

 p. 247. 



In the present work the author investigated the stages of develoiHiient and 

 infection in bean as occasioned by C. lindenmthianum in order to ascertain 

 whether Ihis funsus acts as does .Bofn/tis cinerca. It is stated that the spore 

 of C. liiHlciiiiithianion when germinating on bean produces a germ tube which 

 develops iido a thick-walled, dark-colored appresorium. This attaches Itself 

 closely to tlie surface of the bean pod by the help of a mucilaginous envelope. 

 l<'i'()ni this contact surface a peg-like infection hypha grows out which ruptures 

 mechanically the cuticular layer and brings abont a swelling of the subcuticular 

 layers, supposedly by enzym action, withcmt causing apparently any swelling, 

 disorganizing, or other chemical action upon the cuticle. 



The general conclusion i-eached is that the mechanism of penetration by 

 C. lindemutJikimcm is in all respects similar to that of B. cinerea. 



lilackleg — a destructive cabbage disease, R. E. Vaughan (Cnnner, ^9 

 {1919), No. 2, pp. 59, 60, fif/'^. 3). — Extensive losses were caused in portions of 

 Wisconsin during 1918-19 by cabbage blackleg {Phoma Unyam). No resistant 

 varieties or strains have been found. Seed treatment with corrosive sublimate 

 1 : ."00 i)rovi(les the most satisfactory control measure, thcmgli rotation does 

 nuicli to check the disease. 



The difficulties of growing red clover — clover sickness, and other causes 

 of failure, A. Amos {Jour. Roy. Ayr. Soc. England, 79 {1918), pp. 68-88, figs. 

 5; abs. in Rev. Appl. Ent., Ser. A, 7 {1919), No. 11, pp. Ul, U2).—0t the six 

 groups of caiis'es of failure in clover crops as here dealt with, the author dis- 

 cusses in some detail nematode attack {Tglenchus derastatrix) , stem rot 

 {Sclerot'mia trifoliorum), and the alleged excretion of toxic substances by the 

 clover plant as causing clover sickness. It is concluded that the evidence at 

 hand to date as regards excretion of toxic substances is insufficient. 



Nematode attack is best coniltated by avoiding all crops which are susceptible 

 to this disease for at least eight years. Stem rot disease is also to be combated 

 by I'otation, avoiding for instance the planting of red clover within two years of 

 beans. 



Degeneration in potatoes, O. B. Whipple {Montana Sfa. Bui. 130 {1919), 

 pp. 29, figs. 16). — The results are given of five years' observation and experi- 

 mental work on the possible degeneration or running-out of potatoes. In the 

 course of the experiments selection plats were maintained and planted on the 

 tuber unit and tuber line plan. 



The relation of degeneration to various physiological diseases is pointed out, 

 and in case of spindle-sprout and yellow-top degeneration may take place sud- 

 denly and completely. Mosaic disease does not seem to be unlike curly dwarf 

 in this respect, in which case the plants from a single tuber are either all noi'- 

 mally vigorous; intermediate, or all typically curly dwarf degenerates. Curly 

 dwarf is apparently unlike other forms in that the deterioration takes place 

 gradually. Intermediate types exist that may be readily distinguished from 

 normal vigorous plants. In special seed plats, the intermediate type should be 

 eliminated l)efon> degeneration has advanced to a point where it sei-iously im- 

 pairs yielding (pialities. Foliage characteristics are said to be the most reliable 

 indicators of degen«>ration tendencies. Depth of eyes of the tuber is said to be 

 correlated with degeneration, and efforts to improve the types of existing varie- 



