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Buds at various stages of development were grown for 3 weeks on solid media containing coconut milk, minerals, vitamins, sucrose, and varying quantities of gibberellic acid, indoleacetic acid, and kinetin. The best average growth was obtained on media containing GA at 2.0 mg/liter, IAA at 1.0 mg/liter, and kinetin at 0.05 mg/liter. When results were compared for buds explanted at very young stages and at older stages, however, young buds attained better average growth on media with 0.5 mg/liter of IAA. Evidence is presented for interaction between IAA and kinetin. With buds explanted at young stages, as the kinetin concentration was increased, optimum growth occurred on media with increasing concentrations of IAA. With older buds, on the other hand, as the kinetin concentration was increased, optimum growth occurred on decreasing concentrations of IAA. Bud growth was compared on media with growth substances sterilized by autoclaving with growth on similar media with these substances filter‐sterilized. Better growth occurred generally on the media with filter‐sterilized ingredients. A long‐range objective of this research is the development of a system that would make possible quantitative measurements of floral development in vitro.

The microanatomy of ~~yg~~~~~o~~~~z~~ m~teli from ~~s~el~ mento is described from whole mounts and sections with the use of light microscopy. It is compared with previous descriptions of 0. musteli, descriptions of other members of the genus Orygmatobothrium and a description of Phyllobothrium dohmii; in addition, specimens from Woodland's collection of 0. masteZi were obtained on loan from the British Museum (Natural History) and examined. 0. versatile is regarded as a junior synonym of 0. musteli and the latter is considered the type species. The trivial name versatile cannot be used to refer to any larval orygmatobothrid. 0. musteli as distinguished by Riser (1955) is not a member of the genus Urygmatobothrium, and P. d~hr~ii is removed as a synonym of 0. rnu~tel~. 0. maste~i is considered to be the only species in the genus.

No abstract

Excised floral buds of Aquilegia formosa Fisch. were grown on a coconut‐milk medium containing the minerals and vitamins of Murashige and Skoog, sucrose, and kinetin. The plant growth regulators indoleacetic acid (IAA, 0.5 mg/liter) and gibberellic acid (GA, 2.0 mg/liter) were added singly and in combinations; both were omitted from the control medium. The addition of GA to the basal medium was required to support sepal development on flowers at all phases of development. The formation of stomatal complexes in the epidermis of the sepals occurred only in the presence of GA. Sepals grown in the presence of GA also contained trichoblasts and developing trichomes, while none were formed in the absence of GA. The role of IAA in the development of these idioblasts was not clear but it appeared to have no effect. The hormones GA and IAA had different effects on the growth of the sepals. In the presence of GA the sepals increase in length until comparable with sepals grown in vivo. However, the sepals remained small when GA was omitted from the medium. Upon closer examination of this effect, it was determined that there was a direct proportionality between an increase in cell number in the epidermis and an increase in sepal length. The role of the two hormones in increasing epidermal cell length in sepals was distinct and separate. Exogenous IAA had no effect upon cell division but was required for cell elongation, while GA was required for cell division and had no effect on cell elongation. The GA effect in promoting cell division in the sepals was substantiated by use of autoradiography. If the buds were grown on media with GA, twice as many epidermal cells along the central file incorporated significant amounts of tritiated thymidine. The cell cycle of the epidermal cells of the GA‐treated sepals was ca. 8.7 hr in duration and ca. 13.0 hr if GA was deleted from the medium.