摘要:

The rockweed,F. vesiculosus, inhabits the littoral zone and is exposed for a large part of the time between tides. It is shown that this weed fixes or evolves CO2at a greatly reduced rate when exposed, even if its surface is wet and the atmosphere surrounding it is saturated with water.

ISSN:0008-4026    

DOI:10.1139/b63-015

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

This paper reports the discovery of a community of arctic–alpine plants on the cliffs, rocky ledges, and boulder beaches along the south shore of Old Woman Bay. The site is located on the east shore of Lake Superior at approximately 47° 47′ N. lat., 84° 54′ W. long., in the District of Algoma, Ontario. Reference is made to earlier reports of arctic–alpine plants occurring in the Lake Superior region and to important collections from the north and east shores of the lake already available in herbaria. A description is given of the site at Old Woman Bay and of the plant community discovered there, together with a presence list of 40 species of vascular plants. Collections made at the site are cited in an annotated list and distribution maps with special comments are provided for the following species:Woodsia alpina,Trisetum spicatumvar.pilosiglume, Polygonum viviparum, Sagina nodosa, andSaxifraga aizoönvar.neogaea. A list of bryophytes is also included.It is suggested that the arctic–alpine species reached the Old Woman Bay region by a natural migration during or soon after the retreat of the last glaciers of the Wisconsin stage of the Pleistocene ice age. Later the boreal forest invaded the area but the arctic–alpine species have been able to survive on the rocky shores where suitable habitats with cooler microclimatic conditions prevail. This explanation entails assuming an age for the community in the order of at least several thousand years. The possibility of recent introductions of these species is considered improbable.

ISSN:0008-4026    

DOI:10.1139/b63-016

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Developing buds ofLedum groenlandicumOeder. are studied. By the latter part of May, those that will produce next year's leaves are well advanced, and a month later beginnings of epidermal hairs are present on the leaves. The morphological development of the hairs is traced. Elongate hairs, both multicellular and unicellular, have long, cylindrical, or semicylindrical, vacuolate cells. The elongating cells have a transverse orientation of the cellulose microfibrils in their primary walls as demonstrated by the polarizing microscope. The vacuolate cells of capitate hairs do not become cylindrical, and they lack the regular orientation of the cellulose in their walls. The pectic material does not become calcified, and the hardening of this part of the wall is thus eliminated as a factor in shape control. The abscission of hairs from the upper leaf surface is brought about by a softening of the middle lamella, apparently through a change from pectic acid to soluble pectin rather than by depolymerization. The hairs on the lower surface remain attached, but the walls of their basal cells become cutinized and the hairs are thus isolated from the leaf tissues. An incipient cuticle covers the young leaves in buds collected in November. At this time the linking together of molecules to form cutin has begun, as indicated by the insolubility of the layer in fat solvents, but the bonds must be few, the layer being easily broken down by a solution of sodium hydroxide. The gradually increasing difficulty in bringing about this reaction indicates that, except during the cold of winter, there is a gradual increase in the bonding until late May or early June, when the cuticle is fully formed. Additional evidence was found for the hypothesis that the developing cuticle exerts a deciding influence on the shape of epidermal cells.

ISSN:0008-4026    

DOI:10.1139/b63-017

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The uptake and fixation of S35-labelled sulphate in the rockweedFucus vesiculosushas been examined using direct chromatography of ground tissue as well as conventional techniques. The uptake of sulphate, unlike that of carbonate, is complex and not directly related to internal requirement. Both the uptake and fixation of sulphate are increased by light. Sulphate appears to penetrate into the thallus with difficulty: cut tissue took up sulphate much faster than undamaged tissue, the rate of uptake being roughly proportional to the area of cut surface, not to the area of intact surface. Frozen and ground tissue retained its ability to convert sulphate into organic forms for a short time. An active exchange of the sulphate portion of the sulphated polysaccharide, fucoidin, was detected. The incorporation of S35into fucoidin was 20 to 600 times greater than that of C14, depending on the duration of the experiments.

ISSN:0008-4026    

DOI:10.1139/b63-018

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Sodium acetate-1-C14or (in one case) succinic-2,3-C14acid was fed to both immature and mature leaves of four monocotyledons (lily, oats, philodendron, and tradescantia), three dicotyledons (red clover, petunia, geranium), a gymnosperm (spruce), and a pteridophyte (Boston fern). These experiments have indicated that chlorophyll synthesis and thus chlorophyll turnover in the mature leaves of the monocotyledons is very slow or non-existent. On the other hand, considerable amounts of C14were incorporated into the dihydroporphyrins isolated from the mature leaves of the dicotyledons, the gymnosperm, and the pteridophyte.

ISSN:0008-4026    

DOI:10.1139/b63-019

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

An investigation of the radial growth of jack pine (Pinus banksianaLamb.) defoliated by the Swaine jack-pine sawfly (Neodiprion swaineiMidd.) disclosed that growth rings were discontinuous and missing in cross-sectional disks from severely damaged trees. In young and open-grown trees with dead tops, the incidence of such deficiencies in radial growth was especially high in disks from upper regions of the stems, in the vicinity of the dead tops; radial growth was suspended for 1 year and subsequently resumed in disks from the lower regions of some stems. Cambial inactivity was more generalized in trees from an old and dense stand and it was detected in disks representing major portions of some of the stems sampled; the death of some trees followed 2 to 6 years of cambial inactivity in disks cut at various heights along their entire stems. Growth deficiencies in the young stand were clearly effects of severe sawfly defoliation. Data from the old, dense stand indicated that sawfly defoliation had perhaps merely hastened the gradual deterioration of the stand in which intertree competition was intense.

ISSN:0008-4026    

DOI:10.1139/b63-020

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

A fungus isolated from lesions on leaves ofFragaria virginianacollected near Hudson Hope, B.C., was identified asMarssoninasp. The symptoms of the disease were somewhat different from those produced by theMarssoninastage of the strawberry leaf scorch fungus,Diplocarpon earliana(Ell. & Ev.) Wolf. Differences were also observed in temperature requirements for growth and conidia production, pathogenicity, and size and shape of conidia. It is proposed to give this fungus specific rank and name itMarssonina canadensis.

ISSN:0008-4026    

DOI:10.1139/b63-021

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Moss polsters were collected at 15 sites between Toronto and Lake Timagami, Ontario, and at 4 localities in the Lake Timagami area for the purpose of determining the regional pollen rain and its local variations. Pollen percentages ofAcer, Quercus, Ambrosia, Chenopodiaceae, Compositae, and Gramineae decrease northward andPicea, Pinus, andBetulaincrease at the more northerly sites. From the three most northern sites a regional pollen rain was calculated by averaging the percentages from nine pollen spectra. In this area the regional pollen rain is dominated byPicea(15%),Pinus(38%), andBetula(22%). At one site a grain ofEphedrawas recovered, apparently carried in by long range drift. The nearest place that it grows naturally is in the southwestern United States. Various pollen trap types were investigated and it was found that all types of moss polsters and some types of decaying stumps (depending on their moisture-holding capacity) were effective in preserving the modern pollen rain.

ISSN:0008-4026    

DOI:10.1139/b63-022

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

The ontogeny of the perfect stage inMicroascus longirostrisandM. irigonosporushas been investigated. Sexuality has also been examined inM. longirostris, M. trigonosporus, M. cinereus, andM. doguetii.Results show that all these species are homothallic, and that perithecial formation inM. longirostrisandM. trigonosporusfollows the general pattern outlined by previous workers. The author has been able to clarify at least three important developmental phases which had either been ignored or insufficiently described by earlier investigators. These are the formation of the perithecial primordium; the development of the sterile hyphae of the centrum; and the structure and nuclear condition of the ascogenous system.

ISSN:0008-4026    

DOI:10.1139/b63-023

出版商:NRC Research Press    

年代:1963

数据来源: NRC

摘要:

Descriptions are given of the ovary and ovules, megasporogenesis, embryo sac, endosperm, embryo, and seed coat structure ofEuphrasia arcticaLange,Orthocarpus luteusNutt., andMelampyrum lineareDesr. Although the ovary is usually bicarpellary, syncarpous, and bilocular with axile placentation in the tribe, a tendency toward unilocularity and parietal placentation occurs inOrthocarpus luteus. The number of ovules is reduced to four inMelampyrum lineare. Development of the embryo sac is of the monosporic eight-nucleate type inEuphrasia arcticaandOrthocarpus luteus, but is tetrasporic and seven-nucleate inMelampyrum lineare. No fusion of polar nuclei occurs in the latter. The endosperm isab initiocellular. Nuclear division in the primary micropylar chamber is followed by a vertical wall which remains incomplete. Aggressive haustoria develop at opposite ends of the endosperm. The chalazal haustorium is unicellular and binucleate. The micropylar haustorium is incompletely bicelled, with four nuclei inE. arcticaandM. lineareand two nuclei inO. luteus. InM. linearesix to eight tube-like processes develop from the micropylar haustorium of which one usually enlarges and enters the funicle. The endosperm proper is generally uniform inE. arcticaandO. luteus, but inM. lineareit becomes differentiated into three regions, the massive micropylar part consisting of cells with thickened, prominently pitted walls and the chalazal part of thin-walled cells with large intercellular spaces. Embryo development inE. arcticaandO. luteusresembles that ofCapsella bursa-pastoris, while development inM. linearefollows that ofPolygonum persicaria. EmbryologicallyMelampyrum linearediffers markedly from other members of the tribe.

ISSN:0008-4026    

DOI:10.1139/b63-024

出版商:NRC Research Press    

年代:1963

数据来源: NRC