ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00027.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

SUMMARYThe diatom flora growing on Bryophytic material on wet rock in Brotherton Park, Cheshire has been investigated. In all, twenty‐nine species were found. Comparison of this community with that of soils and permanently submerged Bryophyta suggests that it is independent and highly characteristic in its species composition. Notes are given on some of the most interesting species.I wish to thank Dr J. W. G. Lund for his valuable comments on the manuscrip

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00028.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

SUMMARYThe diatom floras of some calcareous spring and stream samples in a small watercress‐growing area have been examined. Plants and sediments from the springs, and plants, sediments and stones from the streams have yielded a total of 123 diatoms, divisible into distinct communities, the composition of which is discussed. The sediments yield a large number of species with several species co‐dominant. The epilithic samples are poor in species with generally a single dominant. The Rhodophycean algaBatracko‐spermumsupports a very sparse epiphytic flora, whereas that on mosses, in algal felts and on water plants is richer. Comparison is made with data from Denmark, Hungary and the Ba

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00029.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

SUMMARY1The stems of more than 500 species of dicotyledonous plants from 175 families have been examined histologically, using sections fixed in formalin‐acetic‐alcohol and in which the tannins have been made conspicuous by iron salts. The leaves of the same or nearly related species have been examined chemically for leuco‐anthocyanins. In 83 % of the cases the presence or absence of tannins in the stems coincides with the presence or absence of leuco‐anthocyanins in the leaves. It is therefore suggested that the histological reaction for tannins is most commonly due to leuco‐anthocyanins.2In about one‐fifth of the cases where agreement has not been observed, ellagic acid is present in the leaves and it is presumed that ellagitannins are responsible for the staining reactions observed in the stems. In other instances, e.g.Cornus, Sambucus, Passiflora, leuco‐anthocyanins, although absent from the leaves, are present in the stems. The remaining cases are accounted for either by dissimilarity of the species examined (e.g. Santalaceae) or by the presence of constituents which might react with the iron salts although not of tannin nature (e.g. mucilage in Boraginaceae and aucubin‐like substances in Scrophulariaceae).3The tendency of leuco‐anthocyanins and other tannins to be more frequently present in woody plants is confirmed and its significance discussed.4The occurrence of tannins can be used as a taxonomic character, for although these substances are of very widespread occurrence amongst the Dicotyledons, some families are highly tanniniferous, in others little or no tannin has been detected, and a third group of families have given mixed results.5Some of the orders of Dicotyledons, as understood in the Englerian system, tend to produce tannins more freely than others, but there is no more than a limited agreement between the occurrence of tannins and the composition of the orders as understood in any of the well‐known systems of classification.6A very interesting parallelism has been noted between the occurrence of tannins and the phylogenetic status of the families in which they occur as revealed by the ‘advancement index’ assigned to them by the statistical technique developed by Spome. The capacity to synthesize tannins seems to decrease as the advancement index increases.The assistance of the Director and Staff of the University Botanic Garden, Cambridge, in supplying botanical material is gratefully acknowledged. Thanks are also due to the gardens staff at Kew for their collaboration in growing and collecting botanical material. So far as one of us (E. C. B‐S.) is concerned, the work described in this paper was carried out as part of the programme of the Food Investigation Organization of the Department of Scientifi

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00030.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

SUMMARYOur information on the extent and the distribution of the vegetation types on Socotra referable to the arid zone may be summarized as follows:1.Maritime vegetationis present over small areas along the coast of Socotra. The observed communities have been described and similar, or slightly different, ones are believed to exist to a limited extent in other parts of the island which were not seen, such as near Kalansiya and at Shoab and possibly elsewhere.2.Desert vegetation. No vegetation community can truly be ascribed to this type. There are limited gravel and sand stretches on the coastal plain, where the paucity of the vegetation is due to edaphic aridity, and parts of the limestone plateau, where perennial growth is reduced by winds, but the existing vegetation can be described as a debased form of other plant communities reaching the climax under more favourable conditions.3.Subdesert shrub and grasscovers most of the island, i.e. the whole of the southern coast, most of the northern coast and the western and central parts of the limestone plateau.4.Subdesert shrub with treesis another well‐represented vegetation type, comprising the rock communities of the limestone slopes, theBoswellia‐Dracaenacommunity of Homhil and possibly other similarly sheltered parts of the limestone plateau.5.Subdesert scrubis not represented, at least in its typical composition. On the basis of the vegetation cover one might possibly regard the denserCrotonformations as belonging to this type, but this would be atypical in relation to the communities characteristic of this type.6.Subdesert bush and thicket. The mixed thickets of the lower slopes of the Hagghier and some of the sheltered valleys within the limestone region, such as the Goahal gorge can only be ascribed to this type, even though somewhat atypical.7.Xerophilous open woodlandis not represented in its typical composition.8.Vegetation of sites where water is presentincludes numerous riverine communities and the cultivations of Socotra.9.Vegetation of semi‐arid type. The vegetation of the semi‐arid zone is confined to the highlands of the Hagghier, above the height of 850 m., where only two vegetation types can be recognized, the Open grassland and the Evergree

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00031.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00032.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY

摘要:

SUMMARYA normal flower possesses a 4‐merous perianth, an indefinite number of stamens and pistil consisting of two carpels. Variations from this plan have been described and they may be interpreted as instances of reversion.There is a correlation between the variation in the different parts of the flower. An increase in one whorl is accompanied by a corresponding increase in other whorls.Branched stamens were observed in all flowers and bifurcated petals in a few. The occurrence of transitional stages from stamens to petals, petals to sepals, and sepals to bracts suggests the staminodal origin of the floral parts.The replacement of the four‐whorled trimerous perianth by a two‐whorled penta‐merous perianth and ultimately by a two‐whorled 4‐merous perianth is suggested. Meristic variation has resulted from the transformation and displacement of f

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1957.tb00033.x

出版商:Blackwell Publishing Ltd    

年代:1957

数据来源: WILEY