Section 6 — Cytology 



begins replication a little earlier but both arms 

 replicate in a relatively short period. Thus, as in 

 man the X chromosomes in the female replicate 

 asynchronously and the chromatin body is ap- 

 parently derived from the X in which the long 

 arm replicates last. 



6.43. (D.) Effects of Digitonin on Dividing Meriste- 

 matic Cells and Cell Wall Formation. L. V. 



Olah (Carbondale, U.S.A.). 



6.45. (F.) Mitosis with Undivided Chromosomes in 

 Irradiated Cells. Gunnar Ostergren and 

 Jadwiga Mole-Bajer (Lund, Sweden). 



In irradiated endosperm of Haemanthus va- 

 rious disturbances of mitosis occur. An interest- 

 ing deviation consists in nuclei entering into 

 mitosis with undivided chromosomes each con- 

 sisting of a single chromatid only. These are 

 often associated by means of a presumably un- 

 specific pairing mechanism that suddenly stops 

 working with the start of anaphase. 



Demonstration of the mitotic cycle of "digi- 

 tonin" mitosis is represented by a series of micro- 

 photographs. The ultrastructure of "digitonin" 

 mitosis is shown by a series of electron micro- 

 photographs. Alteration of the geometry of mi- 

 tosis and the origin and function of the phrag- 

 moplast is shown by a series of schematic 

 drawings. Phases of "digitonin" mitosis are 

 demonstrated by microscopical slides. 



6.44. Reciprocal Translocation obtained after Col- 

 chicine Treatment in Phlox drummondii. 



T. S. Dhillon (Hong Kong). 



Seedlings of Phlox Drummondii were raised in 

 clay pots. After two to three leaf pairs had 

 developed, the growing points of seedlings were 

 smeared with 0.5 per cent emulsion of colchicine 

 in lanolin. Twenty out of fifty treated seedlings 

 survived and produced main stem from the 

 colchicine treated growing point, as well as 

 lateral branches from nodes below the level of 

 colchicine application. First meiotic division was 

 studied in the PMCs of buds taken from the 

 main stem as well as the lateral branches. Eight- 

 een treated plants and fifty untreated plants were 

 found to be meiotically normal and showed 

 seven bivalents at M.I. Main stem of one of the 

 treated plants was found to be autotetraploid 

 whilst the laterals originating from first two 

 nodes of this plant were diploid. In the remain- 

 ing treated plant, main stem showed an inter- 

 change complex involving four chromosomes 

 and five bivalents. The first and second node 

 lateral branches of this plant were meiotically 

 normal, showing seven bivalents at M.I. Whilst 

 the lateral branches of this plant were completely 

 fertile, the main stem and lateral branches origi- 

 nating from fourth node and above, showed 40 

 to 50 per cent aborted pollen grains and had 

 reduced seed set. 



6.46. (D.) Cytological Studies of Nothoscordon, Al- 

 lium and Molium. S. E. Eid (Shatby, Egypt). 



I. Centromere Structure: Following hydroxy- 

 quinoline treatment of chromosomes of Notho- 

 scordon inodorum (Ait) Asch et Gr., the median 

 centromere could show up to 6 or more pairs of 

 chromomeres. The terminal centromere, being 

 a free end, may have a greater chance for ex- 

 tension, showing up to 8 or more pairs of chro- 

 momeres. At anaphase I the centromere may 

 show two structures directed towards the near 

 pole. These two structures can be seen trans- 

 versely connected. (To appear in Bull, of Faculty 

 of Science, Alexandria University, 1962.) 



II. Effect of the Environment on Meiosis, in 

 Nothoscordon inodorum {Ait.) Asch et Gr. and 

 Some Allium Species: 



A. High temperature treatment of flower 

 buds on Nothoscordon inodorum, leads, in 

 certain cases, to increase of the chromosome 

 number from 19 to 32, in the pollen mother cells. 

 This is attributed to duplication of the 13 meta- 

 centrics but not the 6 telocentrics, of the com- 

 plement. 



B. Cold leads to asyndesis and high tempera- 

 ture may lead to asyndesis or equational division 

 with transitional conditions. (To appear in 

 Journal of Botany of the United Arab Republic, 

 1962.) 



III. Cytological studies in section Molium of 

 the genus Allium. 



6.47. (D.) Chromosome Reconstruction for Studies on 

 Mutagenesis and Other Cytogenetical Problems. 

 I. I. Oster, R. Schwarz and R. Binnard 

 (Philadelphia, U.S.A.). 



Several new stocks and techniques have been 

 devised in order to facilitate studies on muta- 

 genesis and other cytogenetical investigations by 



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