Febkuaey 15, 1907] 



SCIENCE 



265 



tion. Of these, blast, the most serious, is 

 caused by a fungus of the genus Piricu- 

 laria, as the writer has demonstrated by 

 repeated successful inoculations from pure 

 cultures. It is not impossible that further 

 researches will show this disease to be a 

 form of the Italian Brusone. Two diseases 

 are increasingly prevalent, and may have 

 been recently introduced into the country: 

 a 'smut,' caused by Vstilaginoidea virens 

 (Che.) Tak. ; and a stem rot under water, 

 due to Sclerotium Oryzce Catt. 



The Production of Toxic Soil Conditions 

 by the Boots of Plants: Howard S. Reed, 

 Bureau of Soils, U. S. Department of 

 Agriculture. 



The author reported the results of ex- 

 periments demonstrating the excretion of 

 deleterious substances by roots. Roots 

 growing in non-nutrient agar rendered it 

 unfit for further growth. .The excretions 

 from wheat were decidedly toxic to a sec- 

 ond crop of wheat. The excretions from 

 corn or cowpeas were scarcely, if at all, 

 toxic to wheat. The excretions from oats 

 were quite toxic to wheat but less toxic 

 than those of the wheat itself. Apparently 

 the excretions from the roots of a given 

 plant, or of its near relatives, are more 

 toxic to that species than the excretions 

 from plants belonging to more distantly 

 related species. 



The Role of Certain Elements in the Phys- 

 iology of the Plant Cell: Howard S. 

 Reed. 



The author reported the results of ex- 

 periments made at the University of Mis- 

 souri. The vegetative bodies of a number 

 of lower plants were cultivated in solutions 

 lacking one of the essential elements. Most 

 of the elements have more or less specific 

 functions to perform, and, within narrow 

 limits, there is no substitution possible. 

 The view was held that the essential ele- 



ments, in addition to building up tissues, 

 serve as sources of energy to the cell. 



Some Mutual Effects of Tree-roots and 

 Grasses on Soils: Chas. A. Jensen, Bu- 

 reau of Soils, U. S. Department of Agri- 

 culture. 



Seedling trees of maple, dogwood, cherry, 

 pine and tulip were planted in paraffined 

 wire pots and the pots planted to wheat. 

 The pots were of such size as to make a 

 close physical relation of the roots of the 

 two kinds of plants necessary. The pots 

 containing the trees in every instance gave 

 less yields of wheat than the controls, espe- 

 cially during summer months when the 

 trees were physiologically active. Towards 

 the autumn, when the trees were entering 

 upon their seasonal rest, the wheat yields 

 increased, sometimes slightly exceeding 

 those of the controls. Different species of 

 trees also had different effects on the wheat 

 yields. As the experiment was carried on 

 under control of external conditions, it is 

 believed that the bad effect of the tree 

 seedlings on the wheat growth is due to 

 toxic substances excreted by the tree roots. 



The Botanical History, Classification, and 

 some Uses of Sorghum: Carleton R. 

 Ball, U. S. Department of Agriculture. 

 Andropogon sorghum (L.) Brot. com- 

 prises a very large number of domesticated 

 forms. None of them is known to exist 

 in the wild state. The cultivation of 

 sorghum dates from remote antiquity. 

 India and the eastern and central portions 

 of Africa are to-day the two great sorghum 

 centers, both in rich abundance of forms 

 and in the economic use of them. Facts 

 point to the independent origin of numer- 

 ous cultivated forms in India and in Africa. 

 A. halepensis, supposed to be the parent of 

 all cultivated sorghums, is widely distrib- 

 uted over most of these two regions. In- 

 troduction into Europe took place in the 



