218 



SCIENCE 



[N. S. Vol. XLIX, No. 1261 



Tile symptoms of this trouble are very strik- 

 ing. Affected roots turn yellowisli, then pink 

 and dry up. The disease is confined to the 

 roots only and not to the bulb. As fast as the 

 old roots are affected new ones are produced, 

 these in turn becoming diseased. In the end, 

 the bulb spends all its energies in producing 

 new roots -which in turn become affected, thus 

 failing to attain the commercial standard. 

 Diseased bulbs remain dwarfed and small to 

 the end of the season, although apparently 

 sound in every other way. The average an- 

 nual loss from this disease in Webb County 

 may be estimated at forty per cent. 



Careful investigations in the laboratory of 

 the Texas Experiment Station revealed the fact 

 that the disease was caused by an apparently 

 new pathogenic organism, the name of which 

 is proposed to be Fusarium malli, n. sp. Over 

 one thousand plate cultures were made from 

 diseased material and in nearly every case a 

 pure culture of the above organism was ob- 

 tained. Moreover in planting healthy onion 

 sets in both sterilized sand or soil in which 

 a pure culture of the Fusarium fungus was 

 worked in, the disease in each case could 

 readily be reproduced. The symptoms on the 

 artificially infected plants were in every re- 

 spect identical with those of infected plants 

 naturally found in the field. The checks re- 

 mained free, proving that Fusarium malli 

 Taub. is the cause of pink root. 



Numerous laboratory experiments, which 

 were duplicated in the field have yielded re- 

 sults which are briefly siunmarized as follows : 



1. The disease is carried with infected sets. 



2. The disease is carried over from year to 

 year in the soil. Short term rotations with 

 other crops than onions on pink root lands 

 do not starve out the pink root fungus. 



3. Pink root attacks not only the onions but 

 also the garlic and the shallot. It does not 

 seem to attack any other of the liliaceous 

 plants. 



4 Steam sterilizing will kill the fungus in 

 the soil. Formaldehyde at the rate of one 

 pint to twenty gallons of water, per square 



foot will also rid the soil of the causal or- 

 ganism. 



6. Applications of lime will not rid the soil 

 from pink root. 



6. In infected soils liberally fertilized, espe- 

 cially where quickly available plant food is 

 applied, together with proper cultural manage- 

 ment, the crop can be nursed to produce fairly 

 normal yields. In this case the proper fer- 

 tilizer merely stimulates the bulbs in produc- 

 ing new roots faster than the disease can 

 destroy them. 



7. Fertilizers rich in nitrogen and organic 

 matter are especially valuable for use in soils 

 infected with the pink root. 



8. Healthy sets when planted on diseased 

 soils will contract the disease. Likewise, dis- 

 eased sets planted on healthy soils will also 

 yield diseased bulbs. 



^Numerous experiments both in the field and 

 in the laboratory are still in progress and as 

 soon as these are completed a bulletin will be 

 published by the Texas Experiment Station 

 giving a full description of the causal or- 

 ganism and results of the experiments. 



J. J. Taubenhaus 

 College Station, Texas 



a chromosome difference between the 

 sexes of sphierocarpos texanus 



The chromosome group in the cells of the 

 female gametophyte of Sphcsrocarpos texanus 

 is characterized by one large element greater 

 in length and in thickness than any of the 

 other chromosomes in the group. This large 

 element does not appear in the chromosome 

 group of the male gametophyte, but instead 

 there is a small chromosome commonly nearly 

 spherical in form, and unlike anything found 

 in the female. The other chromosomes in the 

 cells of both sexes vary in length. They have 

 the form of rods, usually curved. The chro- 

 mosome number for each sex seems to be 

 eight. In the cells of the female, seven of the 

 eight are similar respectively to seven of the 

 male. The eighth cliromosome of the female 

 (the largest one) seems to correspond to the 

 small chromosome of the male. The condition 

 as to the chromosomes of the gametophytes in 



