260 GENETICS [Bot. Absts., Vol. VI, 



factor for the flower color in Pisum arvense. A second factor, B, together with A, gives 

 rose. A third factor, C, acting together with A, gives violet, while all the three together 

 give purple. B and C in the absence of A are without effect and the flowers are white. No 

 difference has been observed between homozygotes and heterozygotes with respect to flower 

 color. The common white-flowered varieties of peas may usually if not always be aaBBCC. 



The hilum of the violet-flowered individuals (A( A )bb C( J) have an abnormal structure, 



and lack the tracheal tissue. The conduction of nourishment to the ovules is consequently 

 made more difficult, and the plants show a very poor development of the seeds. The abnor- 

 mal structure of the hilum is directly connected with the factor-combination, AC without 

 B. Tabulations of the results of the crosses occupy 19 pages. — K. V. Ossian Dahlgren. 



1777. Thomson, Arthur. The maturation of the human ovum. Jour. Anat. 53: 172-208. 

 3 pi., 18 fig. April, 1919.— The diameter of the human ovum, including the zona pellucida, 

 is about 0.11 mm. The ovum is ovoid, not spherical. The zona pellucida sometimes shows 

 faint concentric lamination, the characteristic radial striation probably occurring only in the 

 later stages of maturation. A distinct vitelline membrane seems to line its inner surface. 

 At the time of the extrusion of the polar bodies, both of which are apparently expelled before 

 the oocyte leaves the Graafian follicle, what appears to be a perivitelline space is in evidence. 

 — The nucleus ranged in size from 0.020 X 0.017 mm. to 0.030 X 0.024 mm. ; a membrane 

 may or may not be present. Within the nucleus are chromatin granules which may be single, 

 paired, in masses, or arranged in threads. The karyoplasm is more finely granular and paler 

 than the cytoplasm. The latter contains vacuoles, often with a granule within, as well as 

 isolated granules. There is evidence of a centrosome. — M. F. Gayer. 



1778. Urban, J. Uber die Grosse der Stecklinge. [On the size of cuttings.] Zeitschr- 

 Zuckerindust. Bohmen 42: 521-526. 1918— See Bot. Absts. 6, Entry 1612. 



1779. van der Plank, G. M. Kruising van Yersey met Zwartbont vee. [Cross of Jersey 

 cattle with black spotted.] Genetica 2: 300. July, 1920. 



1780. van der Wolk, P. C. Onderzoekingen betreffedne den Cocospalm. [Investigations 

 concerning the coconut palm.] Cultura 1918: 1-34. 1918. — See Bot. Absts. 6, Entry 1613. 



1781. von Ri'MKER, K. 42 Sortenanbauversuche im Verwaltungsgebiete des Oberfehls- 

 habers Ost. [Forty-two variety culture tests in Oberfehlshabers Ost.] 72 p. Paul Parey: 

 Berlin, 1918— See Bot. Absts. 6, Entry 1614. 



1782. vox RCmker, K. Die Staatliche Organisation der Sortenpriifung. [State organi- 

 zation of variety testing.] 32 p. Paul Parey: Berlin, 1918.— See Bot. Absts. 6, Entry 1615. 



1783. von Ryx, Georg. Methoden einer exakten Priifung des Fortschrittes bei der Zuc- 

 kerrubenzucht. Paritats- und doppelte Standard-methode. [Methods of exactly testing the 

 advancement in sugar beet breeding. Parity and double standard method.] Zeitschr. Pflan- 

 zenziicht. 7:227-237. June, 1920. 



1784. vonUbisch, G. Anwendung der Vererbungsgesetze auf die Kulturpflanzen. [Appli- 

 cation of the laws of heredity to cultivated plants.] Naturwissenschaften 8: 293-300. 1920. 



1785. von Wettstein, Fritz. [German rev. of: van Wisselingh, C. Uber Variabilitat 

 und Erblichkeit. (Variation and heredity.) Zeitschr. indukt. Abstamm. Vererb. 22: 65-126. 

 10 fig. Jan., 1920. (See Bot. Absts. 4, Entry 3532.)] Zeitschr. Bot. 12: 462-465. 1920. 



1786. Wagner, M. Abbauerscheinungen am Hopfen und Organisation in der Hopfen- 

 ziichtung. [Phenomena in unimproved hops and organization in hop-breeding.] Deutsch. 

 Landw. Presse 1919: 788. 1919. — After experience in a certain hop region ("Neutomischler" 

 region) author urged an organization for hop-breeding, directed from a central office and 



