| Abstract: | A cytological investigation of British members of the orderLaminariales has revealed the presence of a very large X-chromosomein dividing nuclei of female gametophytes and young sporophytesof Saccorhiza polyschides. This chromosome pairs with a smallY-chromosome at meiosis. A chromosome which is conspicuouslylarger than the others has also been detected in the femalegametophytes (and young sporophytes) of Laminaria spp., Chordafilum, and Alaria esculenta. There is some evidence that thisalso pairs with a smaller chromosome. Chromosome numbers determinedduring the work are as follows: Laminaria digitata, L. saccharina,L. hyperborea, L. ochroleuca, Saccorhiza polyschides, hap-loid31 and diploid 62; Alaria esculenta, haploid 28 and diploid56; Chorda filum, haploid c. 28 and diploid c. 56 |
