ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

Abstract.—A study of the water balance in certain selected plants was carried out throughout the year. Among theseSuaeda asphaltica, Zygophyllum dumosum, Erodium glaucophyllum, enidSeseda muricatadiscard their transpiration organs so as to remain dormant when desert conditions supervene;Heliotropium rotundifolium, Haplophyllum tuberculatumandAtriplex Hali‐musincreasingly reduce their transpiring surface; theHaplophyllumand theAtriplexhave the power of withstanding a large water‐saturation deficit: theHaplophyllumand theHeliotropiumhave the power of limiting transpiration, and, lastly,Retama RetamandAnabasis articulate, have an even water balance which shows no large fluctuations of water‐saturation deficit and water‐content.Observations were made at two selected spots; and the way of working was that of Huber, by weighing cut branches.SuaedaandZygophyllumare succulents having the ratio of water‐content to dry weight high, as all other succulents have, though of course not all plants with the ratio high are succulents. They show a low transpiration, the water balance is uneven, and the transpiration limitation incomplete. They show that a low transpiration does not bring about an even water balance and capacity for drought resistance.Suaedais one of the first perennials to dry up.AnabasisandRetamaare xeromorphic leafless plants, physiologically active throughout the year. Their transpiration in relation to surface is small, its limitation small and the water balance even. They are much more independent of external factors than the other xerophytes.Erodium, Reseda, Heliotropium, andHaplophyllumare herbaceous xerophytes, characterized by high transpiration and a great power of limiting it by stomatal movement. The first two do not survive the dry season in an active state: the other two reduce their transpiring surface gradually and can support a large water‐saturation deficit without damage.Atriplexstands apart from the others. Its transpiration is low, while its water‐saturation deficit is the largest attained by any of the plants examined.It is calculated that these plants per annum use the following amounts of water in kilogrammes:–Retama, 1500–3500;Suaeda, 300–400;Salsola rigida, 50–100;Zygophyllum, 30–120;Haplophyllum, 20–40;Heliotropium, 20–30;Erodium, 20–25; andRtvda, 15–20. To obtain 1500 kilogrammes of water a plant ofRetamaspreads its roots through 38–39 square metres of soil, taking up two‐fifths of the rain which falls on it.Abstract.—The last complete list was published in 1883, and subsequent additional records have been made in 1908, 1929, and 1934. The coast‐line stretches from King's Lynn to Yarmouth, and can be divided into the marsh and cliff coasts each with their own especial flora. Marsh coast is found between King's Lynn and Heacham and between Holme and Cley, whilst the cliff coast is found at Hunstanton and in the Cromer neighbourhood. The algal habitats are as follows:–(1) Flint beds off shore at Hunstanton, Brancaster, Blakeney, and Cromer. (2) Peat beds exposed at very low water near Brancaster. (3) Chalk beach at Runton and Cromer. (4) Salt marshes.The total flora is about 290 species and varieties, and the bulk of these are recorded from the salt marshes, whose ecology is therefore of especial interest. The algal habitats on the salt marshes include physiographic features such as the mud ‘steeps’, the salt pans, and the nature of the creek floors–whether shingle or mud. Harbour entrances are rich in luxuriant algae because of the continual flowing current. Evidence was also presented in support of the recognition of a definite pan flora. Fifteen algal communities are described, of which two, thePelvetia‐BostrychiaandEnteromcrpha ctathratacommunities, have not previously been described for any area.The factors controlling algal distribution on the marshes are submergence and emergence, non‐tidal exposure, temperature, salinity, light, substrate, currents, wave action, influence of phanerogams, and influence of animals. A number of species common to Norfolk and rocky coasts (e.g. Isle of Man) are sublittoral in Norfolk and littoral elsewhere, whilst other species exhibit the reverse phenomenon. In most cases these anomalies are to be associated with the differences in local physiography.The sublittoral region contains two formations, the Chalk and Peat bed formations. The littoral region can be divided into the Rocky shore formation containing the chalk beach and flint bed associations, the Sand and Sandy mud formation with two consocies,

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

摘要:

Abstract.—Prof. Stephenson explained that for some time a biological survey had been in progress along the shores of South Africa; the workers working together in groups and making observations a t a series of chosen localities dong the sea‐board from Port Nolloth on the Atlantic in Cape Province to the neighbourhood of Durban in Natal on the Indian Ocean. He explained the direction of the ocean‐currents which influence the coast; and by using the organisms which occur between tide‐levels he showed that the whole coast is divisible into three parts. The genusPatellais particularly useful, the relative abundance of its species, where they occur in association, and the vigour of their growth, affording data.The speaker described the zonation of the shores with regard to the rise of the tide and compared the zones of the South African shores with those of northern latitudes as in Britain, and with those of cora

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY

ISSN:0370-0461    

DOI:10.1111/j.1095-8312.1937.tb00149.x

出版商:Blackwell Publishing Ltd    

年代:1937

数据来源: WILEY