Die G�ltigkeit der MacDonald-Pfitzerschen Regel bei der Diatomeengattung Nitzschia

Wiedling, Sten

doi:10.1007/bf01475635

Cited by 6 publications

(2 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It should be noted that a number of species of diatoms have been reported as having lost their siliceous skeletons in culture, this being followed by variability in cell shape. Wiedling (1941) discusses some of these observations and reports on one of his own on N. Kutzingiana var. exilis Grun., where the skeleton disappeared after the normal form had been cultivated for many years.…”

Section: Development Of the Oval Cellsmentioning

confidence: 99%

“…minor, where the curvature of the girdle allows new valves to be formed as big as the parent ones (Geitler, 1932)-multiplication may take place with constant apical length, or even with increase in length, though such instances are likely to be rare, the Nitzschia of the Plymouth cultures being one of these. Recently Wiedling (1943) ^a s briefly discussed the general problem of size variation in diatoms, mentioning his own observations on various species of Nitzschia, particularly N. subtilis var. paleacea Grun., N. Kiitzingiana Hilse and N. palea var.…”

Section: Development Of the Oval Cellsmentioning

confidence: 99%

See 1 more Smart Citation

The Triradiate and other Forms ofNitzschia Closterium(Ehrenberg) Wm. Smith, FormaMinutissimaof Allen and Nelson

Wilson

1946

J. Mar. Biol. Ass.

View full text Add to dashboard Cite

1. The natural history in culture of the species of Nitzschia originally isolated from the sea by Allen & Nelson (1910) and grown at Plymouth and elsewhere ever since has been studied. It is shown that three main types of cell exist: normal with two arms (rostra), triradiate with three arms and ovals with none. Both normals and triradiates produce ovals by division, and the ovals so produced can multiply to form further ovals, or can grow either two or three arms, generally two, to form normal or triradiate cells.2. Ovals are more readily produced under good lighting conditions than under weak illumination.3. The cell wall is very lightly silicified, and the cells, unlike those of most diatoms, can elongate without auxospore formation. The maximum, and with it apparently the average, cell size of successive subcultures is variable.4. When triradiates are present they may, and frequently do under good cultural conditions, multiply faster than normal cells and finally may almost completely dominate the cultures. Now and again a proportion of the triradiate cells shorten one arm and gradually pass, during successive divisions, into the normal condition. There is a greater tendency for this process to take place in the autumn than at any other time. There was a notable instance in November 1941 when several cultures at Plymouth and at Hull simultaneously produced normals by this method on an extensive scale.5. There is evidence that under unfavourable cultural conditions triradiates tend to be eliminated.6. A cruciform type of cell has appeared occasionally in several cultures, but it has not been possible to obtain pure cultures of it, for the type appears to be somewhat unstable and readily reverts to the other forms. It has, however, persisted for a long time and for very many generations.7. It is shown that the triradiate type occurs in nature, and there is no reason to suppose that it is an abnormal form due to culturing.8. The nomenclature is discussed and it has been decided for the time being to retain the name Allen and Nelson originally gave to it, although there is a possibility that it is a species separate from Nitzschia closterium (Ehr.) W. Smith.

show abstract

Section: Development Of the Oval Cellsmentioning

confidence: 99%

Section: Development Of the Oval Cellsmentioning

confidence: 99%