934 



SCIENCE 



[N. S. Vol. XXX. No. 782 



4. Weft knotting Knotted Lace Coil. 



B. Active and passive elements. 



1. Weft spiral Twisted Coil. 



2. Weft twisting Twisted Coil. 



3. Weft interlacing Interlaced Coil. 



4. Weft looping Looped Coil. 



Mary Lois Kissell 

 American Museum of Natural History 



pusarium wilt of cabbage 



Wilt or " yellows " disease of cabbage, due 

 to an undescribed species of Fusarium, has 

 been known in this department for some years, 

 as a trouble of minor importance, but it is now 

 gaining such headway in some cabbage sec- 

 tions that active measures will have to be 

 taken to combat it. 



Some of the important symptoms are: re- 

 tarded growth, wilting of the foliage, yellow- 

 ing and dropping of the lower leaves. Later 

 the upper leaves are affected and drop off, 

 leaving the stem bare. In some cases one half 

 of the leaf turns yellow while the other half 

 retains its normal green color for a time. 

 Microconidia are present in great numbers in 

 the water-carrying vessels of the living plant. 

 Soon after the death of the plant, pinkish 

 masses composed of macroconidia form abun- 

 dantly on the surface. 



This disease was first observed by Dr. Erwin 

 F. Smith in 1895. Experiments made by him 

 in 1899 point to the soil as the source of infec- 

 tion. In 1900 Mr. W. A. Orton, of the F. S. 

 Department of Agriculture, made field ob- 

 servations on the disease in South Carolina, 

 and isolated the fungus, but did not carry on 

 further work. 



In April, 1908, the writer isolated the fun- 

 gus from some material sent in from the 

 south. During the past summer the disease 

 has been reported from several states. In the 

 kraut district of northern Ohio it has been 

 very destructive. 



Pot experiments were started in one of the 

 greenhouses, to determine the parasitism of 

 the fungus. After the cabbage plants had 

 been growing in the pots for about ten days, 

 pure cultures of the fungus were mixed into 

 the soil, care being exercised not to injure the 

 rootlets. In about three weeks some of the 



plants began to show symptoms of the disease. 

 An examination of the plants a little later 

 showed 83 per cent, of successful inoculations. 

 None of the controls contracted the disease. 

 The fungus was again recovered from one of 

 the diseased plants, fresh soil was secured, 

 young plants set out and inoculated as in the 

 previous case with pure cultures of the Fu- 

 sarium isolated from one of the previously 

 inoculated plants. The greenhouse conditions 

 for these later experiments were very unfavor- 

 able, but a fair percentage of the inoculations 

 were successful. The controls did not con- 

 tract the disease. This disease will be studied 

 further. L. L. Harter 



Bureau of Plant Industry, 

 U. !s. Department of Agriculture 



THE separated blastomeres op centrifuged 



EGGS OF ARB.ACIA 



In recent years embryologists have been at- 

 tempting to find out the role in development 

 played by the visible materials of the egg 

 (pigment, yoU^, oil, etc.) ; whether they are 

 organ-forming materials or merely passive in- 

 clusions. By no means has a uniform con- 

 clusion been reached. 



In the eggs of Arhacia, the experiments of 

 Lyon and Morgan show that the visible sub- 

 stances, by means of the centrifuge, can be 

 thrown into any part of the egg without af- 

 fecting in any way the embryonic development 

 up to the pluteus. The simple experiment 

 which I wish to record adds further proof 

 that the visible substances in this particular 

 egg are not organ-forming materials. Driesch 

 and Morgan have shown that the one half, 

 one fourth, one eighth and one sixteenth 

 blastomeres of the sea-urchin egg are capable 

 of developing into normal but smaller plutei. 

 Lyon further showed in the centrifuged eggs 

 of Arhacia that the visible substances separate 

 readily into four distinct layers and that the 

 first cleavage is nearly always at right angles 

 to the stratification, but some few are parallel 

 to it. The purpose of my experiment was to 

 take those centrifuged eggs in which the first 

 division plane was parallel to the stratifica- 

 tion, separate the first two blastomeres and see 



