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Page number:746 
Remarks (public):It will be observed that cultures of Odontia bicolor may vary in three of the characters used in diagnosis and that its key pattern denotes these possible variations by (1,2) in Column one, indicating occurrence on broad-leaved and coniferous trees, by (1,2) in Column eight, indicating presence or absence of oidia, and by (2, 3) in Column nine, indicating growth rates from moderately rapid to slow. Since provision must be made for all possible combinations of the variable characters, eight key patterns for Odontia bicolor must be interpolated in the numerical key published previously by the author (8). None of these coincide with key patterns of other species included in the key so that, if the insertions are made, no difficulty should be experienced in identifying cultures of O, bicolor.
In practice it is rarely necessary to follow the procedure outlined above to identify the species. Mounts for microscopic examination of mycelium from the culture as it grows on malt agar slants in culture tubes invariably show capitate cystidia bearing the characteristic large caps of crystalline material. No comparable structures have been observed in any species other than Polyporus abietinus, with which cultures of Odontia bicolor were first confused, and Polyporus pargamenus, in both of which the capitate cystidia (Fig. 8) bear small persistent caps of fine crystals quite distinct from those of Odontia bicolor.
Type of Decay
Up to the end of 1952, 184 cultures from decays in living trees belonging to the 13 species listed in Table I have been identified as O. bicolor, These were isolated during investigations in all provinces from Nova Scotia to British Columbia, carried out by the Laboratories of Forest Pathology at Fredericton, Toronto, Saskatoon, and Victoria. The numbers, limited as they are by the hosts studied, by the size of the samples, and by the success in making isolations, give no reliable measure of the incidence nor of the host range but indicate only that the fungus has an extensive geographic and host range. Information on the volume of decay caused by O. bicolor and its importance in comparison with other species that produce decay is available only for Abies. In their study of decay in Abies lasiocarpa and A. amabilis in the Upper Fraser region of British Columbia, Bier, Salisbury, and Waldie (2) reported it (under Polyporus abietinus) as second among the fungi causing butt and root rots, with 5.2% of the infections and 2.2% of the total volume of decay. Basham, Mook, and Davidson (1) in their publication on decays in balsam fir in Eastern North America listed it as second in the table showing the frequency with which different fungi were isolated from butt rots, with isolations from 72 or 12. 6% of all the butt rots from which the causal organism was isolated and identified.
The data accompanying the cultures indicate that the decay caused by Odontia bicolor is confined to the heartwood of butt and roots, the infection taking place through the roots and advancing from them to the basal part of the trunk. The incipient stage has been described by various investigators as pink, red, pinkish brown, or reddish brown, the advanced stage as white, of the pitted, stringy, or feather type, with black flecks, Samples of decay in Abies balsamea, A, lasiocarpa, Picea glauca, P, mariana, and Pseudotsuga taxifolia that yielded cultures of Odontia bicolor have been examined, In all, the color described for the incipient stage has faded, while the color of the more advanced stages appears paler than that of sound wood. Small isolated pits, usually with white fibrous contents, occur and these apparently may elongate and coalesce to produce a stringy rot (Figs, 12 to 14). Black flecks (Figs, 12, 14) are present in all samples, even in the small inconspicuous pockets of decay, and white mycelial felts are common. The characteristic incrusted, capitate cystidia or detached masses of crystals (Fig. 7) are usually observed in mounts for microscopic examination from the black flecks, which are composed of fungus hyphae and disintegrated wood cells, and from the mycelial felts. In final stages of decay, the wood may be completely destroyed, resulting in a hollow butt or trunk.
From the data presented it appears that Odontia bicolor causes a butt rot of considerable importance in a number of broad-leaved and coniferous trees and that it is widely distributed in Canada.
Description type:Culture description 
Description:Description of Culture
Odontia bicolor (Alb. & Schw. ex Fries) Bres,
Key pattern: (1,2) 1 1 1 1 2 2 (1,2) (2,3) 2 3
Cultures examined:
Canada. - Ontario: Barry's Bay, from decay in Pinus strobus, 21349; Beaverton, on Larix laricina, 17746; Lake Timagami, on Betula sp., 17748. British Columbia: Prince George, from decay in Picea glauca, 21049; Skutz Falls, from decay in Pinus monticola, 21032, from decay in Tsuga heterophylla, 21033.
Cultural characters: (Figs, 1 to 3, 9 to 11)
Growth characters. - Growth moderately rapid to slow, plates covered in three to six, usually four to five, weeks. Advancing zone even, hyaline and appressed in narrow zone or, more rarely, with slightly raised aerial mycelium to limit of growth. Mat white, appressed, downy to fine woolly, in some isolates with long, cottony fibers extending from inoculum and growing against side wall of Petri dish after one week, collapsing and disappearing later, occasionally with branching and anastomosing veinlike lines of slightly more compact growth on older part of mat, becoming narrowly zonate after two or more weeks over whole surface or in newer growth only, this appearance resulting from narrow zones of more compact growth within the agar, all so thin as to be translucent. Reverse bleached, imparting milky white color to culture. No odor. On gallic acid agar diffusion zone moderately strong to strong, no growth; on tannic acid agar diffusion zone weak to moderately strong, diameter up to 2.5 cm.
Hyphal characters. - Advancing zone: hyphae hyaline, nodose-septate 1.8-4.6 µm diameter, Aerial mycelium: (a) hyphae as in advancing zone, frequently aggregated into small strands; (b) cystidia numerous, each consisting of a short stalk borne at right angles to parent hypha or terminally, up to 15.0µ in length, narrow, with tip slightly expanded, up to 3.1-5.0µ diameter, bearing cap of coarse, jagged, crystalline material up to 23.0 µm diameter, which usually becomes detached in mounts for microscopic examination ; (c) oidia rare or apparently lacking, about 1.8µ diameter, of varying lengths. Submerged mycelium: hyphae as, in advancing zone.
Taxon name: