ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 603 



V. terrestris, V. uncinata, V. repens, and a Vaucheria sp. The follow- 

 ing results were obtained. 1. The resting nuclei vary greatly in size, 

 according to the species. Those of V. terrestris have a diameter of 

 4-4 • 6 fj. ; those of V. racemosa 2-3 /x. The nucleus has always a distinct 

 membrane, and in the middle is a body resembling a nucleolus. A 

 nuclear skeleton is present, which stains well. 2. The division of the 

 nuclei takes place in waves, so to speak. The separate successive phases 

 are distributed in a certain order along the length of the filament. The 

 first sign of the approaching division is a remarkable increase in the size 

 of the nuclei. The number of the chromosomes is not large. A ring- 

 shaped arrangement of the daughter-chromosomes is often seen. The 

 stage of the telephase has this appearance : two daughter-nuclei, with 

 characteristically distributed chromatin, in the form of a star and with 

 a central opening, are stationed at the poles of the membrane of the 

 mother-nucleus, which is penetrated at the axis by a bundle of connect- 

 ing filaments. At the moment when the central chromatin ring tears, 

 there appears in the interior of the nucleus a roundish body, which 

 stains very deeply, the nucleolus, which has re-appeared. 3. As to the 

 arrangement of the dividing nuclei, the division of a nucleus is not 

 directly connected with the zone of growth. The origin of the wave- 

 like divisions is the result of a certain disturbance in the simultaneity 

 of the division, and is directly dependent on the speed of development 

 of the cell. Similar cases occur frequently in non-cellular plants, where 

 also isolated divisions take place. Such isolated divisions may possibly 

 be found in Vaucherir 



Cytology of Zygnema ericetorum.* — G-. S. West and Clara B. 

 Starkey publish a contribution to the cytology and life-history of 

 Zygnema ericetorum (Kiitz.) Hansg., with some remarks on the genus 

 Zygogonium. In each cell of Z. ericetorum there is normally only one 

 large asile chloroplast, of indefinite outline. It is usually constricted 

 in the middle, and in some cases twisted. There are two large pyrenoids, 

 one in each half of the chloroplast. The latter usually is more or less 

 masked by numerous oil-globules. A low temperature causes the cell- 

 wall to thicken and cysts to be produced. Filaments of the aquatic 

 form grow well in a 0-2 p.c. Knop's solution. Filaments of the ter- 

 restrial form, when placed in water, gradually fragment and become 

 dissociated into short lengths of cells, which, however, may ultimately 

 grow into long filaments. If placed in " 1 p.c. Knop's solution, 

 similar fragmentation occurs, but is longer delayed. When allowed to 

 dry gradually, the filaments fragment into thick- walled "cysts." 



The genus Zygogonium as founded by Kiitzing (1843) is untenable ; 

 and available evidence does not support the retention of Zygogonium on 

 the basis put forward by De Bary (1858) and Wille (1909). 



JUgagropila Formations.! — J. E. Ljungqvist describes peculiar 

 modes of growth of Srytonema, found by him in the Mastermyr bog 

 on the island of Gottland, in the summer of 1896. The species in 



* New Phytologist, xiv. (1915) pp. 194-205 (5 figs.), 

 t Arkiv f. Botanik, xiv. No. 4 (1915) 34 pp. (3 pis.). 



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