ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01703.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01704.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SUMMARY.The examples of rhabdosome development described above clearly suggest that the graptolite colony is far from being a haphazard aggregate of individuals, but behaves as a complex unit of which the pattern is often precisely regulated. This regulation, which is effected through the budded succession of individuals, appears as something comparable with the varying field of growth potential of a solitary organism and perhaps finds its closest parallel among metamerically segmented animals.Branched rhabdosomes typically show great regularity and symmetry in the disposition of their branches, whether these result from the periodic substitution of a stolotheca for a bitheca (as in siculate dendroids) or the production of two buds in place of the normal one bud. All growing points of the rhabdosome react more or less simultaneously and the frequency with which divisions occur is recognized as a specific character. There is commonly a steady decrease in branching potential as the colony approaches maturity and the regularity becomes noticeably less in higher “orders” of branching. Simplification of the rhabdosome by reduction in the number of branches is a “trend” affecting the whole order Graptoloidea, resulting ultimately in the production of a single chain of a limited number of individual zooids.Distinctive also of the Graptoloidea is a regular and progressive variation in the form of the thecae through the colony. In certain species, these changes are mainly in proportion, such as could possibly be related on a growth gradient to absolute size and length of development, but the majority involve a definite change in shape transmitted through a linear budding series. This thecal pattern finds its most complicated expression in the cyrtograptids, where cladia are developed from certain of the thecae after an appreciable lapse of time and yet the change in thecal type in the main branch appears to affect sympathetically and more or less simultaneously all the growing points of many successive

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01705.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SUMMARY.It is considered that many evolutionary changes in plants, including the division of labour and neoteny, result from restricting the site of development of a hereditary property or by moving it to another part of the plant‐body. This principle of transference of function is explained by examples from the flower (especiallySaraca)fruit, seed, leaf, and venation(Ficus)of angiosperms. Systematic morphology should seek to define the original properties, their sites and their transfer

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01706.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01707.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01708.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01709.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01710.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01711.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb01712.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY