File:Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14 (1934) (20500424388).jpg

Title: Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14
Identifier: contributionsfro14univ (find matches)
Year: 1934 (1930s)
Authors: University of Pennsylvania. Botanical Laboratory; University of Pennsylvania. Morris Arboretum
Subjects: Botany; Botany
Publisher: Philadelphia : (s. n. )
Contributing Library: Penn State University
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

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36 PlIYTOPATIlOUMJY (Vol. 27 light, growing more slowly and displaying darker and more varied colora- tion when exposed, even for very short periods, to indirect daylight than when kept in darkness. High humidity stimulates the development of fluff.V superficial growth. Temperature, concentration and kind of nutrient, etc., also affect the appearance of cultures. The continuous nature of tliese environmental variables and the apparently great number of hereditary fac- tors involved make it impracticable to describe in detail all the mycelia studied. Partial descriptions of a few representative mycelia cultured in Petri dishes are presented in table 1, however, to indicate the range and kind of cultural variations encountered during the study. In this table, and in figures 1 and 2, series I consists of cultures stored at a constant tem- perature of 22°* and exposed to electric light, but never to daylight, for a few seconds every 12 hours, while series II consists of cultures stored at room temperature (10° to 25°) and exposed to diffuse daylight for a few seconds every 4 or 5 days. Descriptions of series I were taken on the 19th day and photographs on the 40th day of growth. Descriptions and ))hoto- graphs of series II were taken on the 29th day of growth. From 2 to 20 cultures were made of each mycelium in each series. Cultural characters of each mycelium in each series w-ere consistent in all cases where not other- wise indicated. From the descriptions in table 1, and from the photographs in figures 1 and 2, it is apparent that differences between mycelia may sometimes be large enough to make difficult the diagnosis of wood decay by cultural methods. Identification may be facilitated by culturing on agar slants in ordinary test tubes and by storing cultures where they will be exposed to daylight of low intensity, since these conditions promote the formation of the more or less leathery mat and hasten the appearance of the range of yellow^ tints" (3) typical of this species, but, even under these conditions, occasional mycelia are not readily identifiable on the basis of their cultural characters. The writer has not investigated the microscopic features of the various mvcelia to a sufficient extent to determine their reliabilitv as criteria of specific identity. Hasty and superficial observations indicate, however, that differences in microscopic characters are neither so great nor so fre- quent as are differences in gross cultural characters. A number of mvcelia were noticeablv destructive to the agar, in some spots lowering the level of the surface 3 mm. or more below that of the rest of the culture (Fig. 3, 40K). Such lowering usually was confined to the region near the inoculum, but sometimes occurred in other portions of the culture. This destructive effect upon the agar, and the particular region in which destruction was visible, w^ere quite as characteristic of certain mycelia as were the color and character of growth in culture. In cultures * All temperatures recorded in this paper are in °C. â > H - T "⢠1937) Guilds: Variability ok Polyporus sctiweinitzii 37 i. \ ⦠* -* > s
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Fig. 3. Cultures showing individual diflferem-es between nionos()orous mycelia. Note aporophores in No. 40B and destruction of agar near inoculum in No. 40K. INTENTIONAL SECOND EXPOSURE

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