Some Notes on Fluorescence Intensity

The fluorescent emission spectra for 5 × 10^-6 M p-aminohippuric and p-aminobenzoic acids in mixtures of methyl alcohol and 1,2-propanediol have been determined. The results indicate that at almost invariant dielectric constant the quantum yield of fluorescence is a function of the viscosity of the solvent. The suggestion is made that a collisional quenching mechanism, which involves the rotational diffusion of solvent molecules, is significant in solutions of low viscosity and less so at high viscosities. A prediction, on the basis of the proposed mechanism, of augmentation of the emission spectra of p-aminohippuric acid, after binding to homologous antihapten antibody, is confirmed. A small red shift is also noted at higher viscosities in protein-free solutions or after binding to homologous antibody. It is suggested that, contrary to some interpretations in the literature, a red shift and/or an augmentation of quantum yield of fluorescence may, in specific instances, not be significant of a transfer of the fluorochrome to an environment of lower dielectric constant.     

Contributions to the Morphology of Some Species of Microsorium

Morphology of eleven epiphytic and rupicaulous species of Microsoriumis described. The paleae in the genus are either peltate withthe basal region developing secondarily as a hood over the stalk,or basally attached with auricles on either side of the stalk.The auricles in M. hancockii and M. pteropus develop from singleinitial cells adjacent to the stalk, while in the others nospecialized initial cells occur. Marginal and terminal glandularhairs occur on the paleae, except in M. hancockii and M. pteropusin which marginal hairs are absent. Slender sclerenchyma strands are scattered profusely in theground tissue of the rhizome. The stelar cylinder is dictyostelicand is dissected by lacunae into cylindrical vascular bundles.Leaf traces are multiple strands originating as branches fromthe dorsal median vascular bundle of the stelar cylinder andthe one next to it on each side. Two or three closely placedvascular bundles of the rhizome constitute the vascular connexionto each branch of the rhizome. Venation of the leaf lamina is reticulate with most of the free-endingveinlets entering foliar hydathodes. The juvenile leaves bearhairs similar to the pro-thallial hairs and are spatulate witha medianly placed forked vein. Sori are generally punctiform,but in M. hancockii and M. pteropus spread slightly over theveins, often forming elongated coenosori. Uniseriate (multiseriatein M. rubidum), multicellular paraphyses occur in all speciesexcept M. scolopendria. The spores are monolete and either psilateor granulate. The prothalli develop from 3-5 cells long germ filaments inwhich the anterior cells divide longitudinally and form an ameristicprothallial plate. An apical meristematic cell is formed later,and a cordate prothallus is developed, except in M. hancockiiand M. pteropus in which a definite meristem is never formedand the prothalli are ribbon-shaped and branched. The cordateprothalli possess polypodiaceous hairs: the ribbon-shaped onesare more or less naked and devoid of any midrib. The chromosome number in the species is n = 36 (zn = 72).