During the present investigation, a total of 1579 seed samples of wheat, 1042 of barley, and 1152 of oats (100 kernels per sample), were examined microbiologically for the presence of Fusarium. Of these samples, 402 of wheat, 513 of barley, and 636 of oats originated in the seed inspection districts of Eastern Canada, and 1177 of wheat, 529 of barley, and 516 of oats in those of Western Canada. Isolates of Fusarium were obtained from approximately 41.8% of the samples of wheat (1.5% of the kernels), 76.2% of the samples of barley (3.9% of the kernels), and 79.6% of the samples of oats (5.7% of the kernels) that originated in Eastern Canada, whereas only 13,8% of the samples of wheat (0.2% of the kernels), 36.3% of the samples of barley (0.7% of the kernels), and 38.9% of the samples of oats (1.1% of the kernels) from Western Canada yielded Fusarium. In classifying the different wild types of Fusarium that were obtained from cereal seed the system of taxonomy and nomenclature of Wollenweber and Reinking was chiefly followed, but certain sections of the genus were revised extensively, partly in accordance with Snyder and Hansens' concept of species in this genus. Four new combinations are proposed, namely F. compactum (Wr.) n. eomb., F. lateritium Nees emend. Snyder & Hansen forma cajani (Padwick) n. comb., F. lateritium Nees emend. Snyder &. Hansen forma crotalariae (Padwick) n. comb., and F. oxysporum Schlecht. emend. Snyder & Hansen var. redolens (Wr.) n. comb. A total of 16 species and varieties of Fusarium, classified in nine sections of the genus, was isolated from cereal seed during this investigation. These species and varieties are, namely, F. poae (Pk.) Wr., F. sporotrichioides Sherb., F. avenaceum (Fr.) Sacc, F. arthrosporioides Sherb., P. semitectum Berk. & Rav., F. equiseti (Cda.) Sacc, F. acuminatum Ell. & Ev., F. culmorum (W. G. Sm.) Sacc, F. graminearum Schwabe, F. sambucinum Fuckel, F. sambucinum var. coeruleum Wr., F. lateritium Nees emend. Snyder & Hansen, F. moniliforme Sheld. emend. Snyder & Hansen, F. oxysporum var. redolens (Wr.) n. comb., and F. solani (App. & Wr.) Wr. emend. Snyder & Hansen. F. poae, F. avenaceum, and F. acuminatum were most frequently isolated. F. concolor Rg. and F. sambucinum f. 6 Wr,, that were previously recorded from cereal seed in Manitoba, and three additional species, namely, F. dimerum Penz., F. merismoides Cda., and F. nivale (Fr.) Ces., that may be encountered in the future among isolates from cereal seed in Canada, were also included in this study.

A list of 66 formae speciales of Fusarium oxysporum Schl. emend. S. & H. pr. p. is presented with their synonymy and hosts. Nine of these are new combinations and five are designated as new formae speciales. The present status of formae speciales as a taxon outside of the International Code of Botanical Nomenclature is discussed.

The present investigation was commenced in 1932 and has been continued annually since that time with the object of determining the identity, host range, and geographic distribution of the Fz~sarizr?n species in Canada. Approximately 9000 isolates of Fzrsarizr?tz were studied. These isolates were obtained from 173 species and botanical varieties of plants, 14 species of insects, and 4 of fungi. Of the varlous specles and botanical varieties of plants from which isolates were obtained, 19 were cereals and grasses, 19 were vegetable crops, 15 were fruit crops, 13 were field crops, 52 were ornamental plants, 31 were trees and shrubs, and 24 were common weed plants. Less than 1 % of the total isolates \was obtained from insccts and fungi. Hltho~igh most of the isolates originated in Manitoba, some were obtained from each of the other provinces of Canada except Newfoundland.

The present taxonomic study involved approximately 1200 isolates of Fusarium which were received by the writer from time to time each year during the past 25 years from tropical and temperate regions. The various isolates originated in 59 geographic areas. Approximately 90% of the isolates were obtained from a total of 160 species of host plants which included cultivated and non-cultivated plants. The cultivated plants included the chief agricultural crops grown in tropical and temperate regions, respectively. About 10% of the isolates were obtained from miscellaneous habitats, e.g. soil, water, insects, wood pulp, fowl, dairy products, and human tissue.A total of 26 species, 4 varieties, and 17 formae of Fusarium, classified in 12 sections of the genus, were identified among the isolates. These species, varieties, and formae are: F. aquaeductuum (Radlk. & Rabh. pr.p) Lagh., F. dimerum Penz., F. merismoides Cda. (section Eupionnotes); F. decemcellulare Brick (section Spicarioides); F. nivale (Fr.) Ces. (section Arachnites); F. chlamydosporum Wr. & Rg., F. poae (Cda.) Sacc., F. sporotrichioides Sherb. (section Sporotrichiella); F. arthrosporioides Sherb., F. avenaceum (Fr.) Sacc. (section Roseum); F. semitectum Berk. & Rav. (section Arthrosporiella); F. acuminatum (Ell. & Everh.) Wr., F. compactum (Wr.) Gordon, F. equiseti (Cda.) Sacc, F. longipes Wr. (section Gibbosum); F. culmorum (W. G. Sm.) Sacc, F. graminearum Schwabe, F. heterosporum Nees emend. Raillo; F. sambucinum Fuckel, F. s. var. coeruleum Wr., F. s. forma 6 Wr., F. tumidum Sherb. (section Discolor); F. lateritium Nees, F. l. forma cajani (Padw.) Gordon, F. l. forma crotalariae (Padw.) Gordon, F. stilboides Wr. (section Lateritium); F. moniliforme Sheld., F. m. var. anthophilum (A. Br.) Wr., F. m. var. subglutinans Wr. & Rg. (section Liseola); F. oxysporum Schl. emend. Snyder & Hansen, F. oxysporum var. redolens (Wr.) Gordon; F. oxysporum forma callistephi (Beach) S. & H.; forma cepae (Hanz.) S. & H., forma dianthi (Prill. & Del.) S. & H., forma gladioli (Massey) S. & H., forma lini (Bolley) S. & H., forma lycopersici (Sacc.) S. & H., forma nicotianae (Johns.) S. & H., forma niveum (E. F. S.) S. & H., forma passiflorae Purss, forma pini (Hartig) S. & H., forma pisi (Lindf.) S. & H., forma tuberosi S. & H., forma vasinfectum (Atk.) S. & H. (section Elegans); F. coeruleum (Lib.) Sacc, F. solani (Mart.) App. & Wr. emend. S. & H. (section Martiella).As indicated by the number of geographic areas and habitats from which they were obtained, the six species most widely distributed were F. solani, F. oxysporum, F. equiseti, F. moniliforme, F. avenaceum, and F. semitectum. Five species, namely F. aquaeductuum, F. chlamydosporum, F. arthrosporioides, F. longipes, and F. tumidum, were encountered rarely, each being represented by a single isolate.

A taxonomic study was made of 1348 isolates of Fusarium found in 206 soil samples collected in 1946. Approximately 70% of the samples, or 143, were obtained from 127 localities in Manitoba; the remaining 30%, or 63, came from seven other provinces.Of 25,973 colonies of fungi that developed on the 2060 soil-dilution plates involved in this study, Fusarium accounted for approximately 5%. A total of 14 species and varieties of Fusarium, classified in nine sections of the genus, were isolated; they are F. merismoides Cda., F. poae (Pk.) Wr., F. sporotrichioides Sherb., F. avenaceum (Fr.) Sacc., F. semitectum Berk. & Rav., F. acuminatum Ell. & Ev., F. equiseti (Cda.) Sacc., F. culmorum (W. G. Sm.) Sacc., F. sambucinum Fuckel, F. sambucinum var. coeruleum Wr., F. moniliforme Sheld. emend. S. & H., F. oxysporum Schlecht. emend. S. & H., F. oxysporum var. redolens (Wr.) Gordon, F. solani (Mart.) App. & Wr. emend. S. & H. F. oxysporum, F. oxysporum var. redolens, F. equiseti, and F. solani accounted for approximately 90% of the total Fusarium isolates. F. oxysporum was by far the most prevalent species isolated. With the exception of F. merismoides, all of the species isolated were found previously to be seed-borne by cereals and to be associated with common root rot of those crops.