MACROCYSTS IN THE LIFE CYCLE OF THE DICTYOSTELIACEAE. II. GERMINATION OF THE MACROCYSTS

Macrocyst germination was demonstrated in the five species of the Dictyosteliaceae known to produce these structures. The morphological changes that occurred during germination appeared to be identical in all of the strains examined, showing the following stages: (1) swelling of the dark, contracted content of the dormant cysts, (2) gradual loss of color and reappearance of cells within what previously appeared as a homogeneous protoplasmic mass, and (3) rupture of the heavy cellulosic cyst wall to liberate the myxamoebae. The age of the macrocyst appeared to be the most critical factor in determining whether or not germination would occur, since the cysts in many of the strains needed to age for several weeks or months before germination could be demonstrated. In Dictyostelium mucoroides strain DM-7, upon which the current study was centered, light was necessary to stimulate germination of young macrocysts—a requirement that gradually diminished as the cysts aged. The rate of germination and the temperature permitting germination were also age dependent: older macrocysts germinated more rapidly and at considerably higher temperatures than did young cysts. Although light was not essential for germination in every strain, the results obtained with strain DM-7 seem to be generally applicable to the germination process.     

Studies of cultivated plants in Choco dwelling clearings,Darien, panama

Useful plants and techniques of their cultivation were studied in and around dwelling clearings of Choco Indians in tropical rain forests of Darien, Panama. The population sampled consisted of 115 adult Chocos living at 26 sites along the banks of the Rio Chucunaque and two of its tributaries, the Rio Tuquesa and Rio Chico. The Rio Chico had a higher population density per linear mite of river bank, but less dwelling area per person was kept clear of vegetation. A map of each clearing allowed comparison of the frequency and spatial distributions of useful plants. These data are statistically treated elsewhere. A decrease in both numbers and variety of native plants occurred as commercially important plants were established on a larger scale. Creation of open niches by means of trash heaps became more definite as distance from the riverbank increased; edible plants were often growing in such locations. Present-day agricultural techniques among the Choco may illustrate their agricultural history. A comparison is made with several extant theories of early agriculture. Small-scale, more intensive gardening was noted in village clearings; groups of dwellings may thus have been a cause rather than a result of field agriculture.     

Growth of Enterobacter cloacae in the presence of 25% sodium dodecyl sulfate.

The growth of Enterobacter cloacae in 25% sodium dodecyl sulfate is described. The bacteria appeared to tolerate sodium dodecyl sulfate rather than metabolize it. The process was energy dependent, and cell lysis occurred during stationary phase. Extreme detergent resistance may be characteristic of the genus Enterobacter.