摘要:

Cercospora cruentaSacc, the causal organism of a leaf spot ofVigna catjangEndl., was investigated with respect to (1) its ability to synthesize thiamine, (2) the presence of thiamine in its mycelium, and (3) possible release of thiamine from the mycelium into the medium. The fungus was found to synthesize thiamine from a medium containing inorganic salts and dextrose. The thiamine was found chiefly stored in the mycelium with only a trace in medium in which the fungus had grown for 50 days at 25 °C.

ISSN:0008-4026    

DOI:10.1139/b55-001

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Prasiola stipitatahas been grown from spore to maturity in pure culture. The alga exhibits no specific organic growth-substance requirements. Growth is markedly stimulated by a source of organic nitrogen.

ISSN:0008-4026    

DOI:10.1139/b55-002

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Bivalents, univalents, end-to-end and side-by-side associations, also chromosome distributions to the poles were associatively recorded for each of approximately 2000 meta-anaphase cells of a haploidTriticum aestivumL. It was demonstrated that the distribution of the univalents to the polar groups was not random. An inverse relationship between side-by-side association and bivalent frequencies was also demonstrated, and this formed the first in a series of analytical steps which led to a description of chromosome movement in the haploid. The validity of certain assumptions concerning chromosome behavior was tested using the χ2method; for others, confirmatory observations were made in monosomic cells.

ISSN:0008-4026    

DOI:10.1139/b55-003

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Parenchyma cells of maple wood may live for more than a century though a considerable proportion die earlier. A few cells succumb each year making "heartwood" formation gradual. Post mortem deposits, primarily in the parenchyma cells, account for the deepened color of older maple wood. The pH, water content, and mineral content of the wood do not change appreciably with aging. Maple wood often becomes deeply stained. The stain is due to deposits in the parenchyma cells which, if killed before senescence sets in, produce a post mortem deposit which is darker and larger than that produced by cells dying of old age. Stained wood is distinctly alkaline and contains substantial amounts of minerals which accumulate in the stained region. These regions also have a higher moisture content than normal wood. The consistency with which stain is produced in advance of spreading decay fungi suggests that staining and the related chemical changes exert a considerable influence on decay in sugar maple.

ISSN:0008-4026    

DOI:10.1139/b55-004

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

The titration reactions between zinc, manganese, and iron sulphates and nabam were studied. Except for possibly those with manganese, they were found to involve more than simple precipitations. Manganese ethylenebisdithiocarbamate was found to be relatively water soluble and easily converted to ethylenethiuram monosulphide (E.T.M.) on aeration. The corresponding-pure zinc salt was highly insoluble in water. Aqueous suspensions were relatively non-fungicidal and failed to yield E.T.M. on aeration. Corresponding suspensions in dilute alkali, however, showed increased solubility and fungicidal activity. They converted readily on aeration to a yellow fungicidal product containing E.T.M. The conversion of E.T.M. to an isothiocyanate was demonstrated. It is concluded that the mode of fungicidal action of the zinc and manganese salts is the same as that of the parent nabam. The same mechanism is probably involved with the iron salts. The practical implications of the work and its bearing on the recent isothiocyanate theory are discussed.

ISSN:0008-4026    

DOI:10.1139/b55-005

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Thirteen phylogenetic principles of general or mycologicai application are presented. Adherence to these principles makes it difficult to accept any starting point for the Basidiomycetes other than a primitive ascomycete very close toTaphrinaand parasitic upon ancient ferns. From the ancestral basidiomycete one line led to the rusts and another, via the parasitic Auriculariaceae, to the remaining Heterobasidiomycetidae and the Homobasidiomycetidae. In this second line the trend has been toward increasing saprophytic ability, increasing frequency of clamp connections, and increasing complexity of fruit body. The evolution of the rusts is traced from the taphrina-like ancestor to the higher Melampsoraceae. A generalized phylogeny of the Phycomycetes and Ascomycetes and a chronology of the strictly parasitic groups of fungi are given. It is clear that parasitism, far from being recent and derived from saprophytism, is generally ancient in the fungi; that the Ascomycetes arose from parasitic, aquatic Phycomycetes; and that saprophytism has in general been derived from parasitism.

ISSN:0008-4026    

DOI:10.1139/b55-006

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

Corticium vellereumEllis and Cragin was isolated frequently from rots of various types in living trees ofAcer saccharumMarsh., which indicates that it invades wood already attacked by other fungi. A description of the characters by which cultures ofC.vellereummay be identified is presented. The fungus is heterothallic and of the tetrapolar type of interfertility.

ISSN:0008-4026    

DOI:10.1139/b55-007

出版商:NRC Research Press    

年代:1955

数据来源: NRC

摘要:

The vascular cambium, to use the term in the general sense as designation for the entire meristem producing secondary xylem and phloem, consists of the self-perpetuating uniseriate initiating layer and the derived tissue mother cells. In the dormant condition the cambium in the stems of mature trees is one to four, usually two to three, cells wide. The one to three tangential tiers of cells toward the xylem are made up of xylem mother cells, and the single tier next the phloem is composed of initial cells. On reactivation all cambial cells expand radially. Periclinal divisions soon follow, usually according to a sequence in which the xylem mother cells in the tier contiguous to the late wood are the first to divide and the initial cells last, although some variation occurs. The zone of periclinal division rapidly widens to 100-300 μ in vigorous open-grown trees, the center of activity during this vernal surge of growth clearly being among the dividing and redividing xylem mother cells. Thereafter, from mid-June to August, a continued decline in cell production follows as the zone of xylem mother cells decreases from many tangential rows to few. The initiating layer becomes relatively more important as the center of cell generation, and toward the end of the growing season the initial cells undergo those changes which modify the cellular pattern of the cambium and hence of the derived tissues. Phloem development begins later than that of xylem, and at the end of May the new phloem varies from none to four cells as compared with a xylemward production of 30-60 cells in vigorous trees. Phloem expansion continues at a more or less steady rate from June to the termination of cambial activity in August or early September. The annual phloem increments vary less in width than those of xylem.

ISSN:0008-4026    

DOI:10.1139/b55-008

出版商:NRC Research Press    

年代:1955

数据来源: NRC