Summary Based on measurements of floral parts and experiments, Anchusa officinalis L. is shown to have a distylous breeding system. Dimorphism is found in the style length/anther height ratio, in stigma morphology and in pollen and corolla size. Plants are self‐incompatible but intra‐ and intermorph compatible. Long‐styled plants outnumbered short‐styled in all populations. Stigmas in short‐styled flowers receive a larger quantity of pollen than those of long‐styled.

Flowers of Primula elatior exhibit all the dimorphic traits typical of distyly. The difference in pollen production between pin and thrum flowers is not thought to be caused by the pollen size dimorphism. The percentage of pin pollen which is probably viable exceeds that of thrum pollen. In the population studied the morph ratio is 1:1, and plants are randomly dispersed with regard to morph type. Bumblebees are the main pollinators, and analysis of the stigmatic pollen load in naturally |xjllinated flowers shows that pin stigmas receive many more pollen grains than thrum stigmas. Intramorph pollination is considerable in pins, while thrums are subject to some differential pollination. Emasculation experiments have shown that intraflower pollination in the thrum morph is negligible. Aging of pin flowers has a reducing effect on their total pollen loads, while in thrums there is no change in total pollen load after the first days of anthesis.

Rates of growth, filtration and respiration of the ascidian Ciona intestinalis (L.) were measured in the laboratory in the presence of food (flagellate Rhodomonas sp.) concentrations ranging from 0 to 12000 cells ml-' (0 to 500 pg C I-'). Weight-specific growth rate (dry weight of body parts not including the tunic) increased sigrnoidally with increasing algal cell concentration to 7.7 % d-' Maximum specific growth rate was related to age rather than size. A condition index (C1 = DWw@Wrotal) reflected level of growth. Specdic filtration rate decreased logarithmically with increased algal cell concentration. Weight-specific respiration rate showed a relation to algal cell concentration similar to that shown by weight-specific growth rate. All rates were transformed into units of carbon, and a carbon budget was established for 2 size groups. Assimilation efficiency (AE) was approximately 50% but decreased at the highest carbon concentrations. The amount of carbon assimilated per body unit that was needed to maintain body (not including the tunic) or total (including the tunic) carbon was independent of initial size and amounted to 10 or 16 pg C mg C -' d-', respectively. Gross growth efficiency (GGE) and net growth efficiency (NGE) varied with food concentration and approached a level of 0.23 or 0.78, respectively, in terms of body carbon. In terms of total carbon, GGE was found to be 0.27 to 0.28 and NGE to be 0.79. Costs of maintenance were greater in the largest ascidians, while costs of body growth were equal in the 2 size groups (0.21 to 0.23).

No abstract

No abstract