摘要:

A taxonomic study was made of several North American taxa in the genusAtrichum. The primary emphasis was on the Canadian taxa and a key to the six species (A. altecristatum, A. angustatum, A. crispum, A. oerstedianum, A. selwynii, A. undulatum) and one variety (A. undulatumvar.gracilisetum) of the country is presented.Atrichum oerstedianum, which has been confused withA. undulatum, is added to the moss flora of the United States and Canada. The distribution ofA. crispumis clarified and a detailed study of the species revealed new morphological characters that are useful to distinguish it. A variety ofA. undulatum, the var.altecristatum, is raised to the rank of a species and morphological and distributional data are given to support the status ofA. selwyniias a distinct species. The first chromosome counts are reported forA. selwynii(n = 7) andA. altecristatum(n = 14). Detailed descriptions are provided forA. altecristatum, A. crispum, A. oerstedianum, andA. selwynii.

ISSN:0008-4026    

DOI:10.1139/b69-050

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Forty-six fungi from Dominica, B.W.I., generally called "black mildews", "sooty molds", and "fly specks", and some of their hyperparasites, are listed, described, or discussed. The fungi belong in the families Meliolaceae, Atichiaceae, Microthyriaceae, Asterinaceae, Brefeldiellaceae, Micropeltaceae, Trichopeltaceae, Trichothyriaceae, Nectriaceae, and Dimeriaceae of the pyrenomycetes and in the families Sphaeropsidaceae, Peltasteraceae, Trichothallaceae, Dematiaceae, and Stilbellaceae of the Fungi Imperfecti.Meliola lobeliicola(Meliolaceae),Clypeolella palicoureae(Asterinaceae),Lembosia carludovicae(Asterinaceae), andAsterostomella diplocarpa(Peltasteraceae) are described as new species, andMeliola carludovicaevar.setosaandAsterina melastomatisvar.verrucosporaas new varieties;Cicinnobella tropicalerepresents a new combination. A key to the three species ofClypeolellaknown on Rubiaceae is included.

ISSN:0008-4026    

DOI:10.1139/b69-051

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The nucellus of cotton (Gossypium hirsutum) contains a column of specialized cells which degenerate before the pollen tube reaches the nucellus. The pollen tube grows between the walls of these degenerate cells. The growth of the pollen tube crushes most of these cells but does not cause the degeneration of additional nucellar cells. An electron-dense material is found in the nucellar cell walls associated with the growth of the pollen tube for about one-half the thickness of the nucellus. This material appears to spread in a wave-like fashion from the tube through the walls of the nucellar cells. Both the walls and cytoplasm of the cells do not appear changed after the passage of the material. The dense material never reaches the embryo sac itself.

ISSN:0008-4026    

DOI:10.1139/b69-052

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The ontogeny of stomata is described for 20 species of Papilionaceae. The mature stomata may be paracytic, anisocytic, anomocytic, diacytic, or with one subsidiary cell. The different types occur individually, or are placed side by side even on the same surface of the leaf. In many species the paracytic type is by far the most common, but in some anisocytic or anomocytic types are more frequent than the other types. The diverse types of stomata show mesogenous development. An increase in the number of subsidiary cells takes place either by their division, or by the neighboring perigenes assuming the form of subsidiary cells. Contiguous stomata are normally formed from two or more adjacent meristemoids. However, inLathyrus sativus, in which they are frequent, their formation by "budding" has also been observed.

ISSN:0008-4026    

DOI:10.1139/b69-053

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The spores ofCeratopteris thalictroidesare large (104 × 128 μ), trilete, with a costate exine and devoid of perine. At germination a rhizoid is produced at the proximal pole, followed by a short uniseriate germ filament lateral to it. Formation of a prothallial plate is initiated by longitudinal divisions in the intercalary cells of the germ filament, and soon a strap-like plate is developed. The thallus broadens and becomes spatulate, but is devoid of any meristem. A pluricellular meristem is later differentiated from lateral marginal cells on one side of the thallus away from the anterior region. The meristematic region becomes notched and later cordate. The anterior half of the thallus expands and develops into a broad flat wing while a smaller, often uplifted wing is developed posterior to the meristem. A midrib is formed behind the meristem when the prothalli are ca. 5 weeks old. The mature prothallus is devoid of trichomes, asymmetrically cordate, with a large, spreading wing and a smaller, often curled and cornucopia-shaped wing lifted up from the substratum. The midrib is thin and bears rhizoids and archegonia on the lower surface. Antheridia are restricted to the wings and are common marginally; they are embedded in the prothallial tissue, and consist of a central mass of spermatozoids surrounded by a basket-shaped, thin, basal cell, a narrow ring cell, and a solitary disk-shaped cap cell. The latter opens like a lid at antheridial dehiscence. The first wall formed in the antheridial initial is basket-shaped and the second wall is nearly flat. Development of the embryo is of the common type in leptosporangiate ferns. The first juvenile leaf is naked, with a spatulate lamina supplied by a solitary vein, and associated with the first root. One or two thick multicellular hairs are produced at the base of the second leaf and, in the succeeding leaves, these appendages are palea-like. A stem apex becomes evident usually only after the fourth leaf is developed. All early juvenile leaves are subsessile with entire lamina. The venation becomes reticulate in the second or third juvenile leaf. It is concluded thatCeratopterisis more closely allied toAnemiaandMohriathan to other genera of ferns.

ISSN:0008-4026    

DOI:10.1139/b69-054

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

In four species of planktonic algae both carbon fixation and excretion on an ash-free dry weight basis increase with relative growth rate (K) of the culture measured in log10units. In natural populations percentage excretion values are positively correlated withKvalues; however, environmental factors may be of relatively greater importance and determine the extent of excretion.

ISSN:0008-4026    

DOI:10.1139/b69-055

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The induction of flowering in western red cedar (Thuja plicataDonn.) by gibberellin (GA3) has a quantitative requirement for long-day (LD). However, the strobilus does not develop fully under LD. Full development does occur though, if the photoperiod sequence of short-day (SD) → LD is given after an initial period of 3+ months under LD for induction. For the male, continued development entails a slight expansion and the shedding of pollen. For the female, it involves expansion from a tight 2-mm bud to a 15-mm cone, even without pollination. Cold increased the number of developing strobili, although it did not affect the date of first expansion. GA3concentration had little effect on continued strobilus development under SD or LD. The present study indicates that continued development of the strobilus has a photoperiodic requirement that can be likened to the requirement of SD → LD of some flowers for anthesis. The requirement for SD is quantitative rather than qualitative, an increasing number of short-days will increase the number of expanding strobili, and eventually (18 to 30 months) some strobili will develop even under continuous LD. Continued development of the strobilus will not take place under SD alone, LD must follow. Therefore, the LD requirement in the sequence SD → LD appears to be qualitative in nature. This does not appear to be true for another conifer, Arizona cypress (Cupressus arizonicaGreene). These strobili will develop under SD, but their development is enhanced by the sequence SD → LD.

ISSN:0008-4026    

DOI:10.1139/b69-056

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

As zoospores ofOlpidium brassicae(Wor.) Dang. encyst on host root cells, they retract their axoneme, secrete a cyst wall, and form an adhesive substance that keeps them in place. The axonemal fibrils have been observed within young cysts but disappear later. The host cell forms a papillum that seems to be an inward extension of the host cell wall. In the cyst, a vacuole develops and enlarges while the cyst protoplast moves through the host wall via a central channel in the papillum, penetrates the host ectoplast, and establishes itself within the host cytoplasm. The ectoplast present around the cyst protoplast remains in the cyst, along with parts of the tonoplast, after infection is complete. This information permits evaluation of hypotheses concerning virus transmission by zoospores.

ISSN:0008-4026    

DOI:10.1139/b69-057

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

A study conducted on the grassland of Varanasi (Tropical), has shown that species diversity increases productive efficiency of the ecosystem while dominance makes the system stable, though less efficient for production. These results are contradictory to McNaughton's observation that diversity decreases efficiency and generates community stability, and thus call for further work before generalization for all situations can be drawn.

ISSN:0008-4026    

DOI:10.1139/b69-058

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The inheritance of seedling reaction to root rot, caused by the 514 isolate ofHelminthosporium sativum, was studied in crosses and backcrosses among the barley varieties CI.8969 and CI.8873, which show resistance, and the variety Olli, which is susceptible. The study was carried out under a controlled environment in growth cabinets. The data from reaction tests of F3and backcross families were analyzed by Elston's procedure for testing a one-locus hypothesis, and by Powers' partitioning method. Polygenic inheritance for seedling reaction was indicated, but subsequent experiments showed that seed weight strongly influenced the reaction, which could account for the polygenic interpretation. Based on a drastic reduction of resistance in greenhouse-produced seed, irrespective of seed weight, a high positive correlation of seed weight with resistance in field-produced seed, and other evidence of a similar nature, it was assumed that resistance was related to a principle, present in the seed or on the seed surface, the quantity of which was influenced by seed size and modified by environment. Whether there was a genotypic influence on the quantity of the resistance principle, aside from that affecting seed weight, was not established conclusively. A field study involving the same materials, made in an area known to produce natural root-rot infection, showed that no correlation existed between the disease indices of the entries in the seedling stage in the growth-cabinet tests, and their reaction to the disease in the field. CI.8873 showed field resistance, whereas CI.8969 did not.

ISSN:0008-4026    

DOI:10.1139/b69-059

出版商:NRC Research Press    

年代:1969

数据来源: NRC