摘要:

SUMMARY1Interspecific hybrids have been set up between a diploid species ofCydosorusfrom Ceylon provisionally identified asC. repandulusand three tetraploid species, namelyC. dentatusfrom Madeira,C. parasiticusfrom Ceylon (two forms), andC. svbpvbescensfrom Singapore.2Interspecific hybrids have been set up between certain pairs of tetraploid species, namelyC. svhpubescens(Singapore) xC. sumatranus(Singapore);C. sumatranus(Singapore) xC. jacuhsus(Ceylon);C. jaculosus(Ceylon) xC. subpubescens(Singapore).3In morphology theseF1hybrids both triploid and tetraploid showed complete dominance in the expression of some of the morphological characters in which the parents differ and an intermediate condition in others. The more important characters showing dominance were: creeping rhizome versus erect rhizome, presence of anthocyanin pigment on the rachis versus absence of it, uniform length of the lower pinnae versus gradual reduction in length, presence of glands versus absence of these. The more important characters in which simple dominance wasnotdisplayed (i.e.F1hybrids were intermediate between the two parental types) were: depth of cutting of the pinnae, number of anastomosing veins at the base of the pinna segments (in old plants, cf. footnote to p. 737), length of hairs on the lower surface of the stipe.4All the hybrids obtained, both triploid and tetraploid, showed a high proportion of aborted spores consequent on irregular meiosis. This was clearly evident even in cases where a preponderance of recessive characters in one parent resulted in a hybrid showing a very close morphological resemblance to the other parent. Spore sterility would therefore be an effective means of detecting hybridity in a herbarium specimen.5Chromosome pairing at meiosis has been investigated in all these hybrids in a preliminary way. All show numerous unpaired chromosomes as one factor contributing to spore abortion. In addition, the triploid betweenC. repandvlus(Ceylon) andC. dentaius(Madeira) showed few or no pairs, indicating rather remote relationship between these two species. The other triploids involvingC. repandvluswithC. parasiticusandC. subpubescensrespectively all showed approximately equal numbers of pairs and univalents, suggesting that therepandvlusgenome is represented in each of the two tetraploid species as half the nuclear content. Among the tetraploid hybrids pairing approximating tonpairs and 2nunivalents was found in each of the two combinationsC. subpubescensxC. sumatranusandC. sumatranusxC. jaculosus, suggesting that in each of these pairs of species a diploid ancestor is shared. This ancestor could beC. repandvlusin one or both cases, though the evidence is insufficient to determine this.6Present knowledge of the ecology and geographical distribution ofC. repandvlusis outlined and a method is suggested for searching for the possible existence of other diploids not yet identified.7A comparison is made between theC. parasiticuscomplex in the oriental tropics and the situation already partially elucidated by other workers on theDryopteris spinvlosacomplex in Europe. The resemblance is so close that it seems likely that there are factors operating in tropical floras which are at least as powerful though necessarily somewhat different in kind from those associated with the succession of glacial and inter‐glacial conditions which have so strongly influenced the evolution of floras in temperate region

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb00034.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.tb00035.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.tb00036.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY

摘要:

SUMMARYFrom a review of the literature, the geographical distribution ofBothriochloa ischaemumis presented as is a brief taxonomic history. Fifty‐seven samples of the species from different localities were grown in a uniform nursery at Stillwater, Oklahoma. Herbarium material was made of ten specimens from a random selection of each sample. Both from field notes and a detailed study of the herbarium specimens a morphological analysis was made.From this analysis two morphological types were established and correlated with geographical distribution and chromosome numbe

ISSN:0368-2927    

DOI:10.1111/j.1095-8339.1958.tb00037.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.tb00038.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.tb00039.x

出版商:Blackwell Publishing Ltd    

年代:1958

数据来源: WILEY