The gametophytic chromosome number for the giant senecios (Asteraceae, Senecioneae, Dendrosenecio) is n = 50, and for the giant lobelias (Lobeliaceae, Lobelia subgenus Tupa section Rhynchopetalumi it is n = 14. Previous sporophytic counts are generally verified, but earlier reports for the giant senecios of2n = 20 and ca. 80, the bases for claims ofintraspecific polyploidy, are unsubstantiated. The 14 new counts for the giant senecios and the ten new counts for the giant lobelias are the first garnetophytic records for these plants and include the first reports for six and four taxa, respectively, for the two groups. Only five of the II species of giant senecio and three of the 21 species of giant lobelia from eastern Africa remain uncounted. Although both groups are polyploid, the former presumably decaploid and the latter more certainly tetraploid, their adaptive radiations involved no further change in chromosome number. The cytological uniformity within each group, while providing circumstantial evidence ofmonophyly and simplifying interpretations ofcladistic analyses, provides neither positive nor negative support for a possible role of polyploidy in evolving the giant-rosette growth-form.
Information in the existing literature on some aspects of the collection and statistical analysis of Sedgwick-Rafter cell data appears contradictory, confusing, or absent . Using data from an experimental phytoplankton population as a basis, an investigation of S-R cell procedure has been undertaken with the following conclusions : ,) settling time depends upon the type of preservation and the composition of the sample ; 2) the field counting technique gives more accurate data and is less time consuming than the strip counting technique ; 3) making fewer counts on each of a greater number of S-R cells gives more accurate results than making a greater number of counts on one or several S-R cells ; 4) nonparametric methods offer a more convenient and nearly as efficient a means of detecting statistically significant differences as compared with parametric methods . A method is presented for optimally allocating counts within and among S-R cells for getting an estimator with the greatest precision in the least time .
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