OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XIV. PHYSODERMA CALAMI

Physoderma calami, a chytrid (Phycomycetes), has not been studied or apparently even collected in Europe since 1895 and has never been recorded in this hemisphere. Material widely distributed in herbaria indicated it was a Physoderma but no details save color, shape, and size of resting spores were known. A study of living material from Vermont indicates resting spore germination occurs by dehiscence of a lid and production of a sporangium with zoospores. The latter may form either an epibiotic or “ephemeral” sporangial stage and zoospores, or an endobiotic one, with extensive polycentric thallus bearing turbinate cells along the rhizoids, and, as outgrowths of these turbinate cells, straw-colored, thick-walled resting spores. The latter stage produces dark-brown spots on infected parts of the host.     

OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XI. A PHYSODERMA ON AGROPYRON REPENS

Sparrow , Frederick K. (U. Michigan, Ann Arbor), Joyce E. Griffin , and Robert M. Johns . Observations on chytridiaceous parasites of phanerogams. XI. A Physoderma on Agropyron repens. Amer. Jour. Bot. 48(9): 850–858. Illus. 1961.—A Physoderma has been found in Michigan on Agropyron repens, which produces dark-brown, non-erumpent streaks up to 20 mm (usually 4–6 mm) in length by 0.5 mm in width and very local discoloration of the leaf blades and sheaths. There is no systemic infection, and plants parasitized are normal in size and bear flowers. Resting spores upon germination produce zoospores which may develop either into the endobiotic, poly-centric, resting spore-bearing thallus or into monocentric, epibiotic, ephemeral sporangia. The latter bear either colorless or orange globuled zoospores. These zoospores may give rise to new epibiotic sporangia, or, apparently without fusing in pairs, to the endobiotic system. Comparison with other congeneric fungi reported on Agropyron repens reveals the Michigan fungus to be distinct from them. Whether it can be embraced within Physoderma graminis (Büsgen) de Wild. or other described taxa on grasses awaits the results of future cross-inoculation studies.     

OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XXV. PHYSODERMA JOHNSII SPARROW,A PARASITE OF CALTHA PALUSTRIS L.

The morphology of the endobiotic and epibiotic stages of Physoderma johnsii Sparrow on Caltha palustris is described. Highly characteristic of the endobiotic stage is the formation of numbers of large, narrowly pyriform cells with a tuft of rhizoids at the broader (distal) end. Early developmental features are not included since germination of the resting spore has not as yet been achieved. Reasons for maintaining this taxon distinct from older ones on Caltha palustris are given.     

OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XX. RESTING SPORE GERMINATION AND EPIBIOTIC STAGE OF PHYSODERMA BUTOMI SCHROETER

The development and morphology of Physoderma butomi Schroeter on Butomus umbellalus L., found in Michigan, is followed from germination of the resting spore through formation of epibiotic and endobiotic stages, to resting spore. No evidence for sexuality was found.     

OBSERVATIONS ON WATER LOSS OF SEAWEEDS IN RELATION TO MICROCLIMATE ON A TROPICAL SHORE (GHANA)1

During a 24-hr period (12-13 April, 1966) continuous records of temperature, relative humidity, wind speed, wind direction, salt spray, and evaporative power of the air were made at Nungua beach, Ghana. Water loss from emersed plants of Sargassum vulgare, Bryocladia thyrsigera, and Ulva fasciata was measured during the same period. The daily march of desiccation in these seaweeds follows the curve for evaporative power of the air. At night the 3 species lose relatively little water and very nearly the same percentage in each case. During the day Ulva is most resistant to water loss, Bryocladia next, and Sargassum is least resistant. This behavior is correlated with the upper limits of the zones they occupy on the shore.     

MORPHOLOGICAL OBSERVATIONS ON THE EARLY IMBIBITION OF WATER BY SIDA SPINOSA (MALVACEAE) SEED

The chalazal area is confirmed as the site of initial water entry into prickly sida (Sida spinosa L.) seeds. Very early during imbibition of water, a kidney-shaped area of the seed coat separates from underlying cells forming a blister. This blister may also be induced in dry seeds (both afterripened and nonafterripened) when pressure is applied to the chalazal area. Blisters form more readily on afterripened seeds than on nonafterripened seeds, however, and the event is correlated with an increase in seed coat permeability to water. Immediately beneath the palisade layer of the blister lies a single layer of subpalisade cells. This layer is observed only in the region of blister formation. As the blister separates, the end walls of the subpalisade cells remain attached to the floor of the palisade layer. The subpalisade cells are thereby broken open, and their contents disgorged into the blister lumen. Evidence indicates that this separation of the palisade and subpalisade layers in the chalazal area initiates imbibition of water by prickly sida seeds.     

COMPARATIVE REPRODUCTIVE BIOLOGY OF ACER PENSYLVANICUM AND A. SPICATUM (ACERACEAE)

Pollination mechanisms and floral features affecting reproduction were examined in two closely-related species, Acer pensylvanicum and A. spicatum. Intra-specific crossing experiments, studies of pollen stainability and ovule number, and observations of the flowers in the field revealed that neither species bears functionally hermaphroditic flowers. Three flower-types were found in each species: staminate, pistillate, and a third type that is morphologically hermaphroditic. The latter form sheds viable pollen, but the pistil does not contain ovules. Pollen-ovule ratios of both species are in the range of expectation for a facultatively xenogamous reproductive system. Outcrossing is accomplished by entomophily in both species. A variety of insects from several orders visit the flowers; however bees in the genus Andrena (Hymenoptera: Andrenidae), especially A. milwaukeensis, are considered the most important pollinators of both maple species because of their fidelity to Acer, their intrafloral behavior, and their ability to carry pollen. However, flies are the most abundant visitors to A. pensylvanicum. Apomixis is an important means of reproduction in A. spicatum. Although floral phenology of these maple species overlaps within a geographical region they were never found blooming simultaneously when growing together.     

法希里舞蛛生物学特性的观察

法希里舞蛛在鲁东南沿海地区一年发生1代,以幼蛛或亚成蛛在洞穴内、杂草丛基部越冬。翌年2月中旬出蜇,幼蛛经8龄后于3月上旬成熟。3月下旬开始卵,卵期38.2d,幼蛛期291d,成蛛期123d,雌雄比为5:3。成蛛日食量0.4386g,是多种害虫的重要天敌。     

四种牛首科吸虫染色体的观察

作者对四种牛首科吸早的染色体进行了观察和相对长度的测量。结果显示,假扇盘吸虫的染色体组型为ｎ＝４ｍ＋１ｓｔ＋２ｔ＝６,吴氏似牛首吸虫的染色体组型为ｎ＝４ｍ＋２ｓｍ＋１ｔ＝７,湖北似牛首吸虫的染色体组型为ｎ＝７ｍ＝７,范尼道 佛吸虫的染色体组型为ｎ＝６ｍ＋１ｓｍ＝７。其中,假扇盘吸虫、吴氏似牛首吸虫和湖北似牛首吸虫的染色体数目和组型为首次报道。