摘要:

SUMMARYBryopsis monoicafrom Banyuls appeared to have a heteromorphic biphasic life‐history. Zygotes from anisogametes grew into creeping filamentous germlings (the sporophytic phase) that produced stephanokontic zoids. The stephanokontic zoids directly developed into newBryopsisthalli (gametophytic phase).The cell walls of the gametophytic phase positively stained with zinc‐chlor‐iodine and Congo red, whereas the cell walls of the sporophytic phase di

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00701.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYThe initiation of the cambium in the ray parenchyma of a shoot has been explained by two contradictory hypotheses: (i) the initiation process is dependent on inductive influences arising from the vascular bundles, or (ii) the process is an autonomic one in the sense that the initiation is determined at a very young stage of the shoot and proceeds without influence from other tissues.Experiments in which small pieces of interfascicular tissue have been isolated and replaced in reverse between the vascular bundles in the hypocotyl have shown that the initiation site and the radial polarity must have been determined many days before the first demonstrable mitotic activity had actually occurred. The experiments provided no evidence pointing to the existence of an inductive effect arising from the vascular bundle or an influence from a surface‐dependent gradient on the initiation of the cambium. It is suggested here that the entire initiation process, including fixation of radial polarity, is determined at the primary meristem ring stag

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00702.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYAn analysis of the floral morphology of a number ofPolycarpicae, based on numerous published reports, reveals that the interpretative morphology of the pistils ofWinteraceae, Lactoridaceaeand some associated groups must be based on the assumption that these female reproductive organs are lateral appendages of gonoclads which became laterally concrescent to form a spurious floral apex. Certain anatomical and comparative morphological details are in good agreement with this interpretation. The pistils in question, inserted on the false floral apex, can only be the homologues of ovuliferous cupules as found in Mesozoic cycadopsid gymnosperms. This type of floral organisation and this category of pistil occur in a number ofPolycarpicae, but almost certainly not in all taxa of this assembly, and also in several other angiospermous groups. The implications of this interpretation in the early divergent Angiosperm phylogeny and in the taxonomy of the Flowering Plants are discussed.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00703.x

年代:1971

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00704.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYCalculations on the linear velocity of the flow of exudate in sieve tubes were carried out, using measured average values for the length and cross‐section of the sieve tubes, the surface area and the thickness of the sieve plate, and the number and radius of the sieve pores. Assuming sieve pores free of any obstruction a velocity of flow of 128 cm.hr–1. atm–1through one metre of sieve tube was found to be theoretically possible. With a pressure difference between the intact sieve‐tube members and the exuding ones of at least 16 atm – at an assumed distance of one metre, the fluid mechanical capacity of the sieve pores of theYuccainflorescence would consequently allow an exudate velocity of 20 metres. hr–1. From the rate of bleeding a velocity of the exudate in the sieve tubes of 0.44 m.hr–1was calculated, thus only a small part of the pores need to be unobstructed during bleeding. In a previous study sieve pores appeared to be often traversed by 10–20 protoplasmic filaments of approximately 250 Å diameter. Assuming all the sieve pores obstructed by such filaments, spaced at the observed distance of 1000 Å, calculations indicated that a pressure difference of 5½ atm.metre–1would be sufficient to explain the earlier observed velocity of exudation.It is concluded that the hypothesis of a mass flow of assimilates from the leaves to the top of the inflorescence of a bleeding plant does not encounter serious objections from the sid

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00705.x

年代:1971

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00706.x

年代:1971

数据来源: WILEY

摘要:

P. H. W. A. M. de Veer:Leven en werk van Hugo de Vries, 252 p. Wolters‐Noordhoff, Groningen, 196

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00707.x

年代:1971

数据来源: WILEY