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SUMMARYThis paper reports the results of an experimental study of Cd tolerance in the grass Holcus lanatus L. The responses of plants from a site aerially contaminated with Cd have been compared with those of plants from metalliferous mine sites and uncontaminated sites, using a range of soil treatments and pretreatments to assess the extent to which Cd tolerance can be affected. Responses in H. lanatus have been compared with those for three other grasses, Agrostis capillaris L., Deschampsia cespitosa (L.) Beauv. and Festuca rubra L., collected from the same sites and propagated as clones on their original soil and uncontaminated soil for three years prior to tolerance testing. Overall, a 13% drop in mean tolerance index was observed; even non-tolerant clones showed a loss of tolerance when grown in John Innes Potting Compost. These results suggest that H. lanatus is capable of greater phenotypic adjustment than A. capillaris, D. cespitosa and F. rubra and that Cd tolerance in this species can also be partially induced de novo in clones from uncontaminated sites. In H. lanatus there is also an indication that the clones from mines are more stable in their Cd tolerance than that from the aerially polluted site. Tbe possible evolutionary significance of these observations is discussed.

Both "Hose-in-hose" and "Jack-in-the-Green" morphs of Primula vulgaris are controlled by unlinked alleles dominant to wild-type. In hose-in-hose the sepals are converted to a second whorl of petals; in jack-in-the-green they extend upwards as long sheathing leaves which persist as photosynthetic organs during and after capsule development. Breeding experiments indicate tight linkage between hose-in-hose and the Ss heteromorphy supergene, while jack-in-thegreen is inherited independently. Both morphs may vary in expression depending on the season and on the background genotype. Hybrids' between the two have an intermediate phenotype with a petaloid calyx tipped with leafy lobes.

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