THE CONDUCTIVITIES OF AQUEOUS SOLUTIONS OF GLYCINE,d,l-VALINE,AND l-ASPARAGINE

1. The conductivities of aqueous solutions of glycine, d,l-valine, and l-asparagine have been determined, and comparisons have been made with similar data reported in the literature. 2. On the basis of certain theoretical considerations, calculations of the expected conductivities of aqueous solutions of glycine, asparagine, aspartic acid, and glutamic acid have been made and these data have been compared with similar data obtained experimentally. 3. The dissociation constants of the carboxyl groups of aspartic acid and glutamic acid have been calculated from conductivity data. 4. It is shown that alanine has no effect on the ionic atmosphere of solutions of potassium chloride.     

SOME EPIDERMAL CHARACTERISTICS OF PALEAS OF DICHANTHELIUM,PANICUM, AND ECHINOCHLOA

The apical portion of paleas of the perfect (upper) floret of 11 species of Dichanthelium, 10 species of Panicum, and one species of Echinochloa were examined with a scanning electron microscope. The surfaces of the Dichanthelium palea tips uniformly had simple, rounded papillae, widely spaced in regular rows, whereas the palea tips of most Panicum species had irregularly arranged, compound or aggregated papillae. Unusual epidermal features were observed in P. obtusum, P. hians, and P. hemitomon. The Echinochloa crusgalli palea surface exhibited a pattern of papillae or spicule development similar to that of P. hians. Transverse sections of Dichanthelium palea showed the papillae to be little if at all thickened. An electron beam x-ray microanalysis indicated a high concentration of silicon in the papillae.     

MODE OF ATTACHMENT,HAUSTORIUM STRUCTURE,AND HOSTS OF PEDICULARIS CANADENSIS

Piehl, Martin A. (Botanic Garden, Santa Barbara, Calif.) Mode of attachment, haustorium structure, and hosts of Pedicularis canadensis. Amer. Jour. Bot. 50(10): 978–985. Illus. 1963.—Although long known for European members of the genus, parasitism is documented for the first time for the North American Pedicularis canadensis (Scrophulariaceae) from observations made in the field. Every stand examined showed evidence for parasitism, the haustorial connections being established in the seedling stage. The haustoria, which vary somewhat morphologically, produce direct connection between the xylem of the host and that of the parasite. The great diversity of hosts, involving 80 species from 35 families, suggests that connections may be made to essentially any vascular plant with subterranean parts in proximity to those of the parasite, although some species are parasitized much more frequently than others. In addition, haustorial attachments were found to dead parts of vascular plants and, in single instances, to a fungus and small pebbles. Intraspecific parasitism has also been observed.