_Pomological Collections_, Gustavus B. Brackett, Pomologist in Charge. _Field Investigations in Pomology_, William A. Taylor and G. Harold Powell, Pomologists in Charge. _Experimental Gardens and Grounds_, Edward N. Byrnes, Superintendent. _Foreign Seed and Plant Introduction_, David Fairchild, Agricultural Explorer in Charge. _Forage Crop Investigations_, Charles V. Piper, Agrostologist in Charge. _Seed Laboratory_, Edgar Brown, Botanist in Charge. _Grain Standardization_, John D. Shanahan, Crop Technologist in Charge. _Subtropical Laboratory and Garden, Miami, Fla._, Ernst A. Bessey, Pathologist in Charge. _Plant Introduction Garden, Chico, Cal._, W. W. Tracy, jr., Assistant Botanist in Charge. _South Texas Garden, Brownsville, Tex._, Edward C. Green, Pomologist in Charge. _Farmers' Cooperative Demonstration Work_, Seaman A. Knapp, Special Agent in Charge. _Seed Distribution_ (Directed by Chief of Bureau), Lisle Morrison, Assistant in General Charge. _Editor_, J. E. Rockwell. _Chief Clerk_, James E. Jones. POISONOUS-PLANT INVESTIGATIONS. SCIENTIFIC STAFF. Rodney H. True, _Physiologist in Charge_. C. Dwight Marsh, _Expert in Charge of Field Investigations_. Albert C. Crawford, _Pharmacologist_. Arthur B. Clawson, _Expert in Field Investigations_. Ivar Tidestrom, _Assistant Botanist, in Cooperation with Forest Service_. LETTER OF TRANSMITTAL. U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF PLANT INDUSTRY, OFFICE OF THE CHIEF, _Washington, D. C., April 10, 1908_. SIR: I have the honor to transmit herewith the manuscript of a technical bulletin entitled "Barium, a Cause of the Loco-Weed Disease," prepared by Dr. A. C. Crawford, Pharmacologist, under the direction of Dr. Rodney H. True, Physiologist in Charge of Poisonous-Plant Investigations, and to recommend that it be published as Bulletin No. 129 of the series of this Bureau.