DISEASES OF PLANTS. 49 



to bo spooios of Fnsjiriiiiii. ExiicriiiuMits witli soil tiikon fi'om infestod fields 

 lii-ddiucd the disease, and as the trouble is ai)])arentl.v due to some soil fungus, a 

 lotatioii 1)1" crops, tbe us(> of commercial fertilizers, etc., are recommended. 



Tbc .Mil bur also reports tbe occurrence of Botrytlx imluhi (ui raspberries, 

 causin,t; a jii'a.v mold, and associated with it was the cane wilt rnii,t,'us (Lcpto- 

 s/iliirrid (■(iiiiotln/riinn ) . The occiiiTriK'c of /I ctci-osixiri inn rdriiihilr on spinach 

 leaves, producing the leaf mold, is mentioned, ;ind while the funj^us does not 

 a|)pear to be a ver.v vigorous ]»arasite, .vet the si»ots caused b.v it on tbe leaves 

 depreciate the market value of the spinach to a considerable extent. A bi'ief 

 account is also given of tbe dami)ing off of tobacco plants, which was sus- 

 pected as being due to a Uhizoctonia, but an examination of specimens did not 

 reveal this fungus in any of tbe .voung i)lants. Cultures of diseased material 

 were made, and while the.v never produced any spores tbe scl(>rotia formed 

 i-esembled those attributed to Sclerotinia, and it was thought jtossible that the 

 fungus in this case was a species of that genus. 



In the studies on the Lima bean mildew tbe author reviews the previous 

 investigations, describes the various stages of growth, and reports having found 

 the oosi)ores, thus completing the life cycle of the organism. Attention is 

 called to tbe fact that, aside from notes on the limited distribution of the Lima 

 bean mildew, i)ractically all that is known about it has been worked out by the 

 various Itotanists connected with the station. The microscopical characters 

 of tbe fungus are described at considerable length, and tbe oospores, which tbe 

 author was the first to discover, are found in tbe seed coats and cot.vledons of 

 tbe seeds and to a limited extent in the tissues of the pods, but not in the stems 

 or leaves. Artificial cultures were successfully made, and both couidial and 

 oogonial stages were formed. The presence of the oospores in the seed empha- 

 sizes the necessity for proper selection as a precaution against the disease, 

 but in addition the rotation of crops, tbe destruction ()f rubbish, s]iraying, 

 pro]ier cidtivation, etc., are recommended. A bibliography of literature relating 

 to this fungus completes the account of this disease. 



In continuation of the work of the author in 1904 ( E. S. R., 17, p. 15H), 

 studies were carried on on the downy mildew or blight {Phytophihora 

 iiifc.sttnis) of potatoes, tbe author seeking to determine the means by which 

 tbe fungus first infects tbe vines in the sunnner. the means b.v which it is car- 

 ried over from year to year, the inoculation of the tubers, etc. The author 

 believes that one of the means of primar.v infection is through the contact of 

 tbe lea\('s with the ground at critical wet periods during July and August, when 

 tbe germs of the blight are probably first generall.y available in the soil for 

 infection. While the author has not yet determined from bis own observations 

 whether the fungus is carried over tbe winter in the soil, so far as the observa- 

 tions go they seem to indicate that blight starts earlier and more vigorously in 

 fields that bore a blight-diseased crop the .v<^ar before, and such factors as 

 earliness of i)lanting, situation of land, previous cro]), etc., nnist be considered. 

 Notes are .given on secondary infections, growth in artificial cultures, per- 

 petuation of the fungus, etc., and in connnenting on the delayed appearance of 

 the blight, the author advances the ojiinion tliat its ajvpearance in July and 

 August is to be attributed possibly to the fact that the mycelium from primaiy 

 infections on young, rapidl.v growing tissues remains localized until after vege- 

 tative growth of the host ceases and then renews its activit.v on the ai»pearance 

 of favorable weather conditions. If the primary infections take place, as the 

 author believes, l)y contact of the leaves with the gi'onnd, this would best be 

 aci-omplisbed after the i)lants have attained full growth. 



Plant diseases of the year, W. I'aduuciv. (t'olurado >Sta. lipt. J'JO-J, pp. 



