Thesis (PH. D)--University of Chicago, 1922. / "Private edition, distributed by the University of Chicago Libraries, Chicago, Illinois." "Contributions from the Hull Botanical Laboratory 299." "Reprinted from the Botanical gazette, Vol. LXXIV, No. 4, December, 1922." Literature cited": p. 368.

Three different aspects of plant adaptations to ecological interactions are examined. The first one is in the area of plant breeding systems. The adaptations investigated in this study involved interactions between male gametes competing for fertilizations on the plant Phormium tenax, an agavoid of New Zealand. In this system I discovered a new type of self incompatibility that depends on the levels of competition among self- and cross-pollinated fruits. This mechanism is parallel to cryptic self-incompatibility in which individual self-pollen grains are not as successful as cross-pollen when competing in the same pistil. The competition-dependent abscission of self-pollinations considered here, however, operates at the level of whole flowers. This form of self-incompatibility may allow a high level of outcrossing to be achieved while it assures seed set when pollinations are scarce. The second case focuses on the interaction between a plant of the genus Bursera and its herbivorous crysomelid beetle Blepharida. This Bursera produces terpenes that are stored in networks of canals that run throughout the leaves and the cortex of the stem. When damaged, there is often an abundant release of resins. Blepharida larvae have developed the behavioral adaptations to overcome the secretive canals of Bursera. Before feeding on the leaves they cut the leaf-veins, interrupting the flow of terpenes. By documenting the growth and survival costs of being on plants of different response strength I was able to show that canals can effectively decrease herbivory even against this specialized vein-cutting insect. The handling time involved in blocking the canals slows down larval growth, delays pupation and increases the risk of predation. Chapter III examines a more complex interaction among plants that produce extrafloral nectaries, ants, and homopterans. An alternative model to explain the function of extrafloral nectaries is proposed. According to this hypothesis, the function of these glands is not to attract ants for defense, but to distract them from tending homopterans by giving them a free source of sugar. Different sources of evidence that support this model are discussed.

The response of Canada milkvetch (Astragalus canadensis var. mortonii) to range and forest improvement practices was studied on a stand of mixed-coniferous forest which was clear -cut and burned in 1963 and 1964, respectively. The field studies were conducted on the Hall Ranch of the Eastern Oregon Experiment Station during the summers of 1968, 1969, and 1970. Canada milkvetch, which was virtually absent at the time of treatment, became one of the most important herbaceous species. The cover, frequency, and density of this species rapidly increased from 1965 to 1967; thereafter, these parameters have decreased, even to the levels of 1965 in some cases. The influence of forest canopy and physical site factor s, viz., soil moisture, soil temperature, and hydrogen ion concentration of the soil were studied. Phenology of seedling, root systems, shoot and flower development, seed production and germination were investigated. Studies were also made on the effects of grazing as they influence flowering, plant height, yield and number s of plants. The population parameters which were studied included cover, frequency, and density. The effects of calcium, copper, and cobalt each alone and in all combinations were studied by growing plants in the greenhouse. In addition, nitrogen fixation and the effect of nitrogen upon root nodulation were examined. The environmental parameters that influence Canada milkvetch are soil moisture and temperature for root nodulation and soil moisture for pod ripening. Soil from areas dominated by Canada milkvetch has higher pH values than soils in the forest and lower values than soils dominated by introduced grass species. In the experimental area, the amount of organic materials on the soil can be correlated with the intensity of grazing. Canada milkvetch begins growth shortly after snow melts, flowers in late June and July, and pods ripen in August. Flowering may begin in early June and continue to September, but the ovaries of the flowers produced early or late abort, because pollination occur s only when a medium sized bumble bee (Bombus sp. ) is the most active. This is the only species which trips the flowers of Canada milkvetch.The greatest amount of damage to the reproductive potential of Canada milkvetch is done by a weevil (Apion sp. ) which lives within the developing pod. At least 50 percent of the pods were destroyed by this insect during the summers of 1968 and 1969. Untreated seeds germinate and produce seedlings at the rate of approximately five percent per month. The rate of germination can be greatly increased by moist heat, but the amount of hard seeds remaining decreases and the amount decayed seed increases. The effects of grazing on this species can be evaluated by plant height, dry weight yield per plant, total yield per unit area, and the number of blossoms per flower stalk. Cattle prefer the inflorescences, but graze the leaves and stems along with the associated species at approximately the same intensity of use. On the other hand, big cattle preferentially graze this species from the time it begins growth in early spring until the animals leave the area. Canada milkvetch was always more productive under a grazing regime of cattle only than under a regime of domestic plus wild animals. Because the vegetation of the experimental area is rather low in the successional hierarchy, rapid changes in the values of cover, frequency, and density have occurred. The importance of Canada milkvetch has steadily decreased since 1967 and the relative importance of grasses has increased. Calcium seems to be required for nutrition and nodulation rather than as an amendment to alter the pH of the soil. Low levels of copper and cobalt also increase growth. Further research is required to adequately define the effects of these elements alone and in combination. Perhaps the successional role of Canada milkvetch can be prolonged by adequate fertility. This research provides an example demonstrating that range and forestry improvement must be coordinated and management intensified in order to maximize the biological potential of a given area. / Graduation date: 1971

There is no abstract available for this thesis.

Thesis (M.Sc.) --University of Adelaide, 1956. / [Typewr. copy].

Thesis (Ph. D.)--University of Chicago, 1913. / "Reprinted from the Botanical gazette, vol. LVIII, no. 3." "Literature cited": p. 233-234. Also available on the Internet. Also issued online.

Thesis (Ph. D.)--University of Chicago, 1913. / "Reprinted from the Botanical gazette, vol. LVIII, no. 3." "Literature cited": p. 233-234.

Habilitationsschrift--Hochschule für Bodenkultur, Vienna. / Bibliography: p. 32.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 97-99).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 189-194.