In Argentina, Paspalum quadrifarium Lam. (paja colorada) forms tall dense grassland communities in the flooding pampas. Referred to locally as "pajonales", these grasslands generally have very low nutritional value for cattle, except at the post-burn regrowth stage. To improve forage quality and consumption by breeding cattle, Lotus tenuis Walst et Kit. is over seeded immediately after burning of paja colorada pajonales. The objectives of this experiment were to follow the after seeding cover of lotus, evaluate weed control, and assess disease incidence and severity. The experiment was carried out in Azul, Buenos Aires province of Argentina, between September 1993 to September 1996. The postburn seedbed was very favorable for lotus germination and establishment. The most effective chemical weed control was obtained with 2,4-DB used alone or in combination with dicamba. L o t u s increased markedly the quality of the pasture forage due to its high crude protein content. Four fungus diseases were found: Botrytis cinerea Pers., S t e m p h y l i u m sp. Wallroth, Uromyces loti Blytt. and F u s a r i um spp. Link ex Fr. However, these caused only light foliar damage and did not impair lotus germination or establishment. The overseeding of lotus after burning of P. quadrifarium pajonales, is a very effective technique to improve carrying capacity and animal performance.

To establish the feasibility of hybridization between the wild carrot species Daucus pusillus Michx. (2n = 2x = 22; 2n = 2x = 22 and 20), collected in the pampas grasslands of Argentina, and the edible carrot, Daucus carota L. (2n = 2x = 18), controlled pollinations were attempted on the plant. Due to the difficulties encountered, flowers of 12 accesions and three commercial cultivars were excised from individual plants and pollinated in Petri dishes following an incomplete diallel design. After processing, the pollinated pistils (four to six per genotypic combination) were observed under a microscope with UV light. Pollen tubes reaching the ovaries and/or the ovules (compatible relation) were observed in six out of nine D. pusillus · D. pusillus and seven out of 18 D. pusillus · D. carota genotypic combinations. In the eight D. carota · D. pusillus genotypic combinations, only ungerminated pollen, pollen not adhered to the stigmas or pollen tubes overlapping the stylar tissue were observed. Additional flowers were pollinated in a sample of compatible genotypic combinations and the pollinated pistils were in vitro culture to study embryo and endosperm development. Eight out of nine pistils from the intraspecific and nine out of 13 from the interspecific crosses enlarged to form apparently normal schizocarps. Histological analyses revealed normal development of embryo and endosperm. The breeding barriers between the two species are incomplete, making feasible the obtainment of interspecific hybrids by conventional techniques.

Three wild carrot species have been reported in the argentinian flora: Daucus montanus Humb. et Bonpl. ex Schult., D. montevidensis Link ex Sprengel and D. pusillus Michx.There is a discrepancy among authors about the distinctive morphological traits of the last two species; thus, it is difficult to ascertain if they are truly two distinct taxa. Based on the available literature and in the search of a paradigmatic site, four collection trips were carried out in 2004 and 2005 in Buenos Aires and Southern Entre Ríos provinces. Populations were sampled at 30 sites, and local environmental parameters and associated plant species were recorded. Morphological observations and chromosome counts were carried out on 10 plants/population. Three morphological phenotypes were distinguished: one in 18 populations, all with 2n = 2x = 18, and two in the remaining 12, with 2n = 2x = 22 or aneusomaty (2n = 2x = 20, 22). Populations of the first phenotype were assigned to wild D. carota and the rest, tentatively, to D. pusillus (D. montevidensis?), till further evaluations are carried out in test sites to verify this tentative conclusion.

Changes in total biomass and botanical composition in a native pasture of the Flooding Pampa in the Salado River Basin (Province of Buenos Aires), under 3 graxing systems: spring-summer rest (November, December, and January); fall rest (April, May, and June), and continuous graaing were evaluated from October 1979 to August 1981. A variable stocking rate based on available forage was used. Total aboveground biomass was periodically sampled to ground level and separated into dead and green components. The green biomass was subdivided into individual species. Total aboveground biomass averaged 4,600 f 445 kg l ha-' and 3,750 f 120 kg l hat for the spring-summer rest treatment during the first and second years, respectively. In the same period, warm-season species increased, principally due to an increase in daiiisgrass (Puspulum dilotrrum Poir.) and bluestem (Botiuio& loa laguroides Herter) biomass. Total aboveground biomass yield was 2,000 f 170 kg* ha-' during the fall rest treatment, and cool-season species such as Poa spp. and Stipa spp. increased. In general, continuous grazing at a moderate intensity resulted in total aboveground biomass of about 2,000 kg DM l hat throughout the experimental period. Contributions of warm-season and cool-season species did not change. Only West Indies smutgrass (Sporobolus indicus (L.) R. Br.) increased under continuous grazing.

Crocidura in captivity. A cta theriol., 24, 5: 61-68. -D ip p en aar N. J. (1979). N otes on th e ea rly p o st-n a ta l developm ent and b eh av io u r of th e tin y m u sk sh rew Crocidura bicolor Bocage, 1889 (In sectívo ra : Soricidae). M am m alia 43: 83-92. -Fons R. (1972). L a m usaraigne m usette, Crocidura russula (H erm ann, 1780 Study of th e seasonal v aria tio n in th e stom ach co n ten ts of coney rats, R eithrodon a uritus (Fischer, 1914), collected in a n a tiv e g rasslan d of th e so u th e ast of Buenos A ires P rovince, show s th a t diet of th is sm all ro d en t is exclusively constitued of p la n t m a terials, m ostly grasses. L olium m u ltiflo ru m and Poa spp. w ere tw o d o m in an t species w hich com posed a 74%> of th e stom ach contents dry w eight. T he n u m b er of item s found in th e diets w ere d ram a tic ally low er th a n th e n u m b er of species in th e p asture. Plant Composition of Coney Rat's (Reithrodon auritus) Diet S K Ł A D D IETY R O Ś L IN N E J U REITH RO D ON AU R IT U SO