Vegetative nuclear structures and their mode of division inCyathus species

Vegetative nuclear division in the homokaryotic and dikaryotic hyphae ofCyathus olla Brodie,C. setosus Brodie andC. bulleri Brodie was investigated. In the homokaryotic hyphae a nucleolus develops within a globular condensed nucleus consisting of a folded up filament. As the nucleolus increases in size, the nucleus unfolds and can assume a ring, horseshoe or filament configuration. The filament duplicates and (usually when unwound from the nucleolus) divides longitudinally. Occasionally, strand separation occurs while the filament is wrapped in the form of a ring around the nucleolus. The daughter nuclei may condense before the next division. In the dikaryotic hyphae the same nuclear cycle occurs as in the homokaryons except that an extra nuclear condensation to the globular form can occur in both the clamp and tube nuclei. The division of these two nuclei is not always synchronous and, moreover, the stage of karyokinesis of the clamp nucleus is not closely synchronized with the formation of the clamp connection. A deeply stained granule is associated with the nucleus. Some granules can be observed to be connected to the nucleus by a faintly Feulgen positive thread-like structure but other granules are sessile. The granule or centriole-like body is thought to direct the nuclear unfolding process. It may divide prior to, or after nuclear division.     

Folic acid as a dietary factor affecting the wing morph of the planthopper, Laodelphax striatellus (hemiptera, delphacidae)

A factor effecting the production of brachypterous adults in Laodelphax striatellus was studied by comparing a diet on which brachypterous adults sometimes developed and a diet on which they never developed. By substituting components distinctive of the latter diet into the former, or by varying the concentration of certain components of the latter diet, the production of brachypterous adults was found to vary with the concentration of a vitamin, folic acid. Brachypterous adults were produced only when the diet contained folic acid at concentrations between 0.5 mg/l and 7.5 mg/l.

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Résumé Un facteur efficace pour la production d'adultes brachyptères chez Laodelphax striatellus a été recherché en comparant une nourriture sur laquelle des adultes brachyptères se développent parfois et une nourriture sur laquelle ils ne se développent jamais. En substituant les constituants spécifiques de cette dernière par ceux de la première ou en variant les concentrations de certains des constituants de la dernière on a montré que la production d'adultes brachyptères varie avec la concentration d'une vitamine, l'acide folique. Ceux-ci sont produits seulement lorsque l'alimentation contient de l'acide folique à des concentrations comprises entre 0,5 mg/l et 7,5 mg/l.