Growth and demography of a declining,endangered cactus in the Sonoran Desert

Increases in the incidence and severity of drought threaten the viability of rare plants in arid regions. The endangered Nichol's Turk's head cactus (Echinocactus horizonthalonius Lemaire var. nicholii L. Benson) occurs only in four small, isolated populations in the Sonoran Desert of North America. Since 1995 we have monitored a population in southeastern Arizona (USA). Here we report 23 years of observations on abundance, growth, mortality, flowering and recruitment. Abundance of plants decreased from 132 in 1996 to 40 in 2017, with 100 individuals recruited and 203 dying during the study. Individual plants grew slowly, increasing annually by an average of 0.22 cm (95% confidence interval, 0.18–0.26 cm) in diameter and 0.27 cm (0.20–0.33 cm) in height. Growth was slowest when drought was most severe and slowed as plants reached maximum size. Annual mortality increased markedly across the study period and did not vary with plant size. Annual probability of flowering increased as plants increased in diameter but not in height, and varied with precipitation and drought but not with mean annual temperature. Recruitment was higher when average temperature was higher and the number of recruits per capita increased across the study period. The annual rate of change in abundance averaged −6%, but shifted markedly from −1% during 1995–2008 to −11% during 2008–2017. Our results indicate that the population's decline was not a consequence of failed recruitment but of increased mortality, which we discuss in the context of climate and herbivory.     

The Distribution of Halogeton Sativus (L.) C. A. Meyer in Morocco

In the search for natural enemies of Halogeton glomeratus (Bieb.)C. A. Meyer, a noxious weed introduced into the United States,studies were made, in 1959-61, on the distribution of H. sativus,a closely related species, occurring within Morocco. This plantis found in the Rif Mountains in the north, throughout the MoulouyaRiver Valley, along the Ziz River Valley, scattered along thesouthern slopes of the High Atlas Mountains as far west as Amerzgane,with an apparently discontinuous area of distribution on thenorthern slopes of the High Atlas in the vicinity of Asni.     

Effect of an Aldosterone Antagonist (Spironolactone) on Patients with Severe Congestive Heart Failure

Spironolactone was evaluated as a diuretic in the therapy of six patients with chronic severe congestive heart failure, during which metabolic balance studies were performed. Two of the patients showed a clear-cut although moderate diuresis and natriuresis in response to spironolactone in the presence of other diuretics. Two patients had slight unsustained responses and two showed no response. No significant change in potassium excretion was observed. A decrease in the serum sodium level was noted in four patients, associated with a rise in serum potassium. Urinary aldosterone excretion was normal or low in all patients and showed no correlation with the diuretic response to spironolactone.It is concluded that spironolactone has definite but limited usefulness in the therapy of some but not all patients with chronic congestive heart failure.