The vascular plant collections of R. S. Williams from Bolivia and Peru (1901–1902): Addenda et corrigenda

Notes that augment an earlier essay on R. S. Williams’ botanical activities and the distribution of his collections from Bolivia and Peru are presented. Twelve species based on Williams’ vascular plant collections are added to a catalog that was previously published. Synonymies of an additional 22 taxa are corrected or updated. Notes also are provided concerning the typification or orthography of two species.     

Organic matter mineralization in the pore water of a eutrophic lake (Aydat Lake,Puy de Dôme,France)

The chemical composition of the pore water from the sediment of a eutrophic lake is dominated by high concentrations of total dissolved CO₂ (up to 12 mM), reduced soluble iron (up to 2 mM) and dissolved silica (up to 1 mM). The pH lies within the range of 6.70 ± 0.02; this reflects that the pore water is efficiently buffered by the CO₂ acid/base system. This composition is directly related to the main diagenetic reactions which drive the organic matter mineralization i.e. methanogenesis and ferric oxides reduction. Other geochemical processes are of minor importance. A stoichiometric model based on these main reactions allow us: (i) to define a general formula for the organic matter which is close to Redfield's one for the C:N ratio, while the C:P ratio is much higher owing to a probable adsorption of phosphorus onto reactive surfaces of the solid and due to heterotrophic bacterial uptake; (ii) to calculate a global first order kinetic constant which drives the organo-polymers breakdown. Due to the strong influence on the trophic status of the lake caused by an excess of phosphate, special attention is devoted to this species. We show that the sediment-water interface is a source of dissolved phosphate when the hypolimnion is anoxic between May and November. This contribution represents about 17% of the river input and should be taken into account in any attempt toward lake restoration.     

Foliage terpenoids of Chinese Cupressus species

Foliage of trees from five Chinese Cupressus species was analysed for volatile monoterpenoids, sesquiterpenoids and diterpenoids. Multivariate analysis of the terpenoid data indicated that C. gigantea is most distinct, but otherwise no obvious chemotaxonomic groupings were evident. Comparison of the Cupressus analytical data with that of specimens of five Chamaecyparis species indicated that Cupressus funebris should not be reclassified into Chamaecyparis.