de Terra, Noël, and E. L. Tatum. (Rockefeller Inst., New York, N. Y.) A relationship between cell wall structure and colonial growth in Neurospora crassa. Amer.Jour. Bot. 50(7): 669–677. Illus. 1963.—Cell walls were isolated from morphological mutants of Neurospora crassa and from their corresponding wild‐type strains. Acid hydrolysates prepared from these cell walls were then studied, qualitatively and quantitatively, with respect to their reducing sugar content. Paper chromatography revealed the presence of glucose and glucosamine in the cell walls of all strains studied. Quantitative analysis has shown that a group of 4 colonial mutants which strongly resemble each other in morphology all have significantly less glucose and more glucosamine per unit weight of cell wall than do their corresponding wild‐type strains. These data strongly suggest that a particular type of morphological aberration in Neurospora is associated with similar changes in cell wall composition.

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The large ciliate Stentor coeruleus lends itself well to microsurgical procedures. By combining these techniques with autoradiography after exposure of cells to thymidine-H3, it is possible to study mechanisms regulating the occurrence of macronuclear DNA synthesis during the cell growth cycle. Transfer of nuclei between cells which are synthesizing DNA and cells which are not can indicate whether DNA synthesis is determined by the continuous presence or absence of a cytoplasmic factor. Similar experiments involving cell grafting could characterize such a factor as an initiator or an inhibitor. This paper describes these experiments and their results.Previous work on Stentor has suggested that mechanisms regulating the occurrence of several major events in the cell growth cycle are located in the cytoplasm.3-5The present results will be discussed in terms of these earlier findings and also in relation to current knowledge about regulation of nuclear DNA synthesis.Stentor coeruleus is a large heterotrich ciliate; individual organisms often reach a length of 1 mm when fully extended. Figure 1A shows the main morphological features of S. coeruleus, including the chain macronucleus, the anteriorly placed oral apparatus, and the rows of blue-green pigment granules running longitudinally between the kineties.Throughout interphase, the macronucleus exists as a chain of nodes spiralling almost the entire length of the organism and situated directly beneath the ectoplasm. At 20'C, amitotic division takes approximately eight hours. Tartar has assigned numbers to the stages of amitotic division.25 There are eight stage numbers, each covering a successive one-hour interval so that stage 1 designates the first hour of division while stage 8 refers to the eighth hour, during which cytokinesis occurs. The macronucleus undergoes a series of striking morphological changes during amitotic division. At stage 5, the nuclear nodes begin to coalesce until the nucleus is a compact mass in the center of the cell (stage 6 ; Fig. 1B

L-Sorbose, an agent which induces colonial growth in Neurospora crassa, also induces structural changes in the cell wall. Acid hydrolyzates of cell walls isolated from sorbose-grown (colonial) hyphae contain more glucosamine and less glucose than do hydrolyzates of cell walls obtained from normally growing hyphae. Snail digestive juice, an agent which effects a structural change in the cell wall of N. crassa by liberating from it large quantities of glucose, has been found to induce colonial growth.

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