摘要:

Four new species ofDictyostelium, all with sorophore bases of a unique crampon‐like pattern, are recognized among 25 isolates obtained from samples of soil and leaf litter collected in forests of Panama, Mexico, Costa Rica, Florida, and Texas. The species described are as follows:D. rhizopodium, characterized by frequently clustered sorocarps with yellowish to grayish olive sori and yellow or brownish purple sorophores;D. coeruleo‐slipeswith white or cream‐colored sori and purplish blue sorophores;D. lavandulumwith grayish lavender to drab vinaceous sori and vinaceous purple sorophores; andD. vinaceo‐fuscumwith deep vinaceous gray to dark smoke‐colored sori and lavender sorophores.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10673.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

A model which visualizes a species as a set of biotype subsets is useful when considering the degree of fitness and homogeneity of populations in their environment. Underfounder principleconcepts we expect that the number of such subsets tends to decrease as local populations encounter new selective forces in environments and habitats other than those occupied by predecessor populations. Relations between biotypes, considered from the point of view of “variation associated with character correlation” or correlated response and polygene systems, imply that the magnitude of product‐moment correlations between characters can be used as a general measure of selective stress impinging upon populations. Magnitude is defined as the per cent of the total possible pairs of characters whose correlation coefficients are significantly different from zero. The direction of magnitude expected under the founder principle is from low in an undisturbed or ancestral situation to high in an alien one. This hypothesis is demonstrated in the genusFroelichia(AMARANTHACEAE).

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10674.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Fourteen collections of gametophytes ofSchizaea dichotoma, corresponding to the broadest taxonomic circumscription of the species, are described from New Caledonia. The gametophyte is subterranean, mycorrhizic and non‐green. It is basically filamentous with uniseriate growing points each ending with an apical cell with a single transverse cutting face. Cells of apical cell derivation divide to produce packets of cells which usually stand out as distinct joints in the older fleshy cylindrical axis. Branching is frequent, initiated as singular cellular bulges at the acropetal ends of the joints, and results in a bushy appearing plant. Thinner, non‐septate rhizoids are produced in the same position as branches. Antheridia are typically schizaeaceous and are produced on short antheridiophores, one to several on each. Archegonia are produced in the same position as antheridiophores and vegetative branches. They are rather ordinary save for the terminal knob formed by the bulging of the four terminal neck cells and the distinct jacket which lines the venter and most of the neck canal. The possible phylogenetic relationship between the uniseriate filament and fleshy axis derived ontogenetically from a multicellular apical meristem is discussed in the context of the Schizaeaceae and vascular plants in general.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10675.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

The genusLiatris(Compositae) affords a favorable vehicle for an analysis of ecological and spatial isolation and their relationship to hybridization. Three biotically sympatric species,L. aspera, L. cylindracea, andL. spicata, were found within a northeastern Illinois sand prairie. Distribution of the threeLiatrisspecies was clearly related to a series of elevation, soil moisture, organic matter, exchangeable cation, and available phosphorus gradients.Liatris asperaoccupied the upper slopes and ridge tops which were high in potassium and phosphorus content but low in moisture, organic matter, calcium, and magnesium levels.Liatris spicataoccurred on the lower slopes and depressions with high soil moisture, organic matter, calcium, and magnesium levels but low potassium and phosphorus content. The third species,L. cylindracea, was restricted to the intermediate mid slopes. These distributional belts intergraded and created broad zones of overlap with opportunities for hybridization. The extent of hybridization was related to the spatial association of species and the availability of intermediate habitats. Hybrids had relatively narrow habitat preferences, and as such, few of the available spectrum of habitats along the elevational gradients were suitable for their establishment.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10676.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Phosphate uptake abovepH 6.0 followed the concentration of H2PO4. Sulfate studies were used to aid evaluation of phosphate data. Phosphate absorption was nearly linearly proportional to transpiration atpH 4.0; atpH 8.7, phosphate absorption occurred only early in the experiments. It was inferred that phosphate entered as H2PO4; that which entered atpH 8.7 did so as the result of a depressedpH at the absorption sites.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10677.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Comparative ultrastructural investigations of the effects of 0.005mcolchicine on the organization of cellular components inChlamydomonas eugametoswere made at intervals during and after treatment. Periodic observation of colchicine‐treated cells revealed curling of the Golgi cisternae and increased vesicle production by the Golgi apparatus, followed by a continuous increase in number of that organelle. Elongated mitochondria were observed to bo an early, but transitory, response, as was a marked proliferation of the nuclear envelope and endoplasmic reticulum; the latter was followed by an increase in nuclear size and convolution. Colchicine‐treated cells also manifested stratification of cell walls and replication of many cellular components. Nuclear anomalies, cytoplasmic compartmentalization, and unusual associations of several organelles were also observed. Initial manifestations of recovery were reorganization of the stigma granules and alignment of cytoplasmic vacuoles. Electron microscopy ofapparentlyrecovered cells indicated their organization to be similar to that of the controls.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10678.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Well‐preserved fresh‐water algae, fungi, and parts of insects have been described from the rich oil shale beds of the 50‐million‐year‐old Eocene Green River Formation of Wyoming, Colorado, and Utah. Recently the sporangia of two additional aquatic fungi, both members of the Chytridiales, have been identified. These sporangia are so nearly identical with those of living species of chytrids (Entophlyctis lobataWilloughby and Townley andPleotrachelus fulgensZopf) that they are assigned to these two genera.E. willoughbyiandP. askaulosare established as new species. Because of the “mummified” condition of these fossil chytrids, the inferred fossilization process is discussed briefly.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10679.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Two mutant strains ofNeurospora crassafailed to grow at 32 C in a minimal medium in which they grew well at 25 C. Both grew in the medium at 30 C after a relatively long lag phase, although the amount of growth at the maximum stationary phase was much less than in similar cultures incubated at 25 C. The addition to the minimal medium of relatively high concentrations of polyethylene glycol “400” or of any one of several sugars or inorganic salts increased growth of each strain at 30 C and enabled each to grow to a limited extent at 32 C. Concentrations of NaCl, polyethylene glycol “400” and glucose most favorable for growth at 30 and 32 C were inhibitory at 25 C. The osmotic pressures exerted by the media containing optimum concentrations of NaCl, of polyethylene glycol “400” or of lactose for the growth of each strain at 30 or at 33 C were within the same general range. Possible explanations of the effects of increased osmotic pressure of the medium upon growth of the strains at elevated temperatures are discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10680.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Study of the time course of regeneration around a wound in internode number 5 ofColeusshowed that first recognizable developing sieve tubes appear 2 days after wounding. Xylem cells appear 3 days after wounding in intact plants and 2 days after wounding in isolated internodes and internode stumps. Xylem cells regenerate on the same radii with previously existing sieve tubes. Separation of xylem from phloem by a cover slip in the cambial zone at the beginning of the experimental period resulted in formation of radially aligned xylem cells and sieve‐tube strands on the phloem side of the cover slip. The results indicate that IAA moves basipetally in the phloem or cambium. The relationship between causal factors in normal vascular differentiation and in the regenerating vascular system is discussed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10681.x

出版商:Wiley    

年代:1967

数据来源: WILEY

摘要:

Nodal explants of the LSD plantCestrum diurnum, each consisting of a short piece of stem with leaf and axillary bud, produced flower primordia in culture on White's basal medium after removal from stems grown on 16‐hr day and subjected to 8‐hr daily photoperiods. No flower primordia formed in the absence of leaves or with leaves excised during the rapidly expanding phase of growth. The presence of 1/16 of a leaf blade was, however, enough to provide for floral initiation. Young mature leaves induced flower initiation equally well whether the leaf was erect, with only the stem portion in contact with the agar culture medium, or inverted, with the leaf blade making contact, whereas, when erect, fewer older leaves induced flower initiation and tended, in addition, to abscise. In a survey involving light intensity (1–1000 ft‐c) and number of daily cycles (1–9) flower primordia were induced to form on 1 ft‐c with 1 short day, increasing percentagewise to an optimum of about 81 ft‐c in 7 days. The number of flowers per bud was little affected by light intensity but increased progressively with the number of daily cycles.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1967.tb10682.x

出版商:Wiley    

年代:1967

数据来源: WILEY