Thesis--Eberhard-Karls-Universität zu Tübingen. Vita. / Includes bibliographical references (p. 76-81).

Thesis (doctoral)--Friedrich-Wilhelms-Universität zu Berlin, 1890. / "Separat-Abdruck aus Bot. Centralblatt 1890, Bd. XLII, No. 20-25."

Some aspects of the role of mosses in the biogeochemical cycle of a coastal forest ecosystem in British Columbia were studied using radioisotopes. The average concentration of ¹³⁷ Cs from atmospheric fallout in ground-dwelling mosses was 36.7 pCi/g or 6025 pCi/m². Concentrations increased with precipitation, with the highest concentrations being found in Plagiothecium undulatum (Hedw.) B.S.G. and Sphagnum squarrosum Crome. Experiments involving a dual labelling with ⁸⁵Sr and ¹³⁴Cs indicated that nutrients which are leached from stem tissues of host plants, and those in the crown washings of the overstorey trees are sources of nutrients for epiphytic mosses. Epiphytic mosses were efficient in filtering radioisotopes from solution, the activity of through-fall and stemflow being reduced after passage through epiphytic mosses by up to 70%. ⁸⁵Sr and ¹³⁴Cs concentrations in ground-dwelling mosses under western hemlock trees (Tsuga heterophylla (Rafn.) Sarg.) followed the distribution pattern of throughfall nutrients which decreased from close to the stem towards the crown edge. / Forestry, Faculty of / Graduate

Thesis (doctoral)--Universität Bonn, 2006. / Downloaded and printed Sept. 10, 2008. Includes bibliographical references (leaves 134-168). Also available via the internet.

Thesis (Ph. D.)--University of Chicago, 1919. / "Private edition, distributed by the University of Chicago Libraries, Chicago, Illinois." "Reprinted from the Botanical gazette, vol. LXIX, no. 6, June 1920." "Literature cited": p. 491.

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Thesis--Dorpat.

Thesis--Wisconsin. / Includes bibliographical references (leaves 98-102).

Thesis (Ph. D.)--University of Chicago, 1913. / "Reprinted from the Botanical gazette, Vol. LVIII, No. 1." Includes bibliographical references. Also available on the Internet.

The primary purpose of the present work was to examine meiosls in mosses, concentrating on the detail of prophase I, a meiotic stage which has been described in detail only in Pleurozium schreberi. Secondarily, an investigation was undertaken to study the effect of heat stress on meiosls. Hypnum circinale Hook, and Brachythecium frigidum (C.M.) Besch. were used to study meiosis. The procedure of preparing spore mother cell squashes was similar to that used by Steere et al. (1954), with modifications in handling the plants prior to fixation to ensure against production of heat induced anomalies. Except for late prophase I, meiosis in both species conformed to that found in P. schreberi. In H. circinale and B. frigidum diplotene was followed by chromosome elongation and resulted in a diffuse stage. This stage is morphologically analogous to the dictyotene stage of the growing oocytes of many animals, and appears to have been described, in plants, only in Balsamina hortensis. It is probable that the stage occurs in many moss families; at present its functional significance is unknown. In the heat stress experiments, plants of H. circinale were either maintained under laboratory temperatures while being studied or they were treated with a heat shock over a period of four or six hours with the maximum temperature in the general ranges of 25°C., 31°C., and 36°C. The maximum temperature was maintained for 4 hours in the 25°C. experiment and 1/2 hour in the remaining experiments. The heating and cooling gradients were almost equivalent (1°C./5 min.), and the starting and finishing temperature was 14°C. The temperature of the natural environment during the study ranged between 7-ll°C Severe anomalies, including chromosome clumping and multiple association, precocious disjunction, chromosome contraction, spindle breakdown and inhibition, premature meiotic induction and meiotic abortion were observed to some extent in spore mother cells from all treatments except the ones from the 25°C. heat shock experiment. Room temperature accelerates prophase I stages of H. circinale. The time available for these stages appears to be too brief for synthesis of necessary products leading to active stages, thus causing severe abnormalities which result in abortion of meiosis. On the basis of these results, it is apparent that cytologists working with moss material should take care in handling the plants prior to fixation to ensure against heat induced meiotic anomalies. / Science, Faculty of / Botany, Department of / Zoology, Department of / Graduate