The symptoms of streak, consisting mainly of ring spotting and systemic necrosis, are given in detail on Nicotiana Tabacum L., Lycopersicon esculentum Mill., Nicotiana glutinosa L., N. rustica L., N. sylvestris Speg. & Comes, N. Langsdorffii Weinm., N. Bigelovii Wats., Nicandra Physalodes (L.) Pers., Datura Stramonium L., Antirrhinum majus Linn., Calendula officinalis Linn., and Phaseolus vulgaris Linn. var. humilis Alef. It was found impossible to transmit streak to Physalis angulata L., Phytolacca americana L., Capsicum frutescens L., Nicotiana glauca Grah., Callistephus chinensis Nees, Petunia hybrida Vilm., and Sinningia speciosa Benth. & Hook.The incubation period varied from 6 to 14 days and 4 to 10 days when transmitted by patch-grafting and juice transfer methods, respectively.It was found that the streak virus was killed in juice extracts at 53 °C. for 10 min. and in patch sticks at 55 °C. for five minutes, but was viable in patch sticks after treatment at 50 °C. for 15 min. Experimental evidence indicates that streak does not overwinter in the soil under Ontario conditions and that little, if any, mechanical spread occurs under field conditions.Circumstantial evidence has suggested that under field conditions streak may spread from sweet clover to tobacco; this is supported by experimental evidence in that streak was transferred from sweet clover to tobacco and a disease resembling streak was transmitted from tobacco to sweet clover.