1434 PLAN^ BREEDING 



The large number of well defined characters which differentiate the 

 two varieties rendered this material exceptionally favourable for the 

 study of coherence, b}' which is meant the tendency for characters associat- 

 ed in one parent of a hybrid to remain together in the later generation of 

 the hybrid. 



Por the study of correlations ii characters were selected in which 

 the parent varieties showed little or no overlapping. The correlation coef- 

 ficients of all the combinations were calculated, and it was found that, out 

 of 55 possible combinations, 20 exhibited significant correlations. There 

 was not a single case in which the correlation between two characters 

 was closer than 0.5, a fact which in itself offers an explanation of the diffi- 

 culty of recognizing types in maize. 



This lack of coherence of characters in maize, coupled with the fact 

 that in order to maintain a satisfactory- degree of vigour diversified ances- 

 tr\' must be maintained seems to render the method of isolating types 

 inapplicable to this plant. As an offset to the limitation thus imposed, 

 advantage may be taken of the facihty with which desirable characters 

 derived from different parents can be combined. 



Appended is a bibliography of 11 works. 



1070 - Number^ of Chromosomes and Size of the Nucleus in Some Forms of An- 

 tirrhinum. — Breslavetz. Iv., in Tpi/Obi Biopo no npuKMtdHou EomaHUKio 

 (Bulletin of Applied Botany), gth 3'ear, No. 6 (91), pp. 381-287 (English text pp. 288-293). 

 Petrograd, June, 19 16. 



As cytologists rarely have at their disposal pure material of non-h}'- 

 brid origin, and as much importance is attributed to the nucleus and chro- 

 mosomes in the transmission of hereditary characters, the number of chro- 

 mosomes in pure lines of certain plants and in their hybrids have been de- 

 termined. 



The researches were carried out with pure lines of Antirrhinum majus, 

 A. lati folium and A. tortuosum, and also with hybrids of the first and se- 

 cond, and the first and third. The cells used were taken from the flower 

 buds, 280, 84, 56, 19, 25 being examined from each variety in the order 

 cited. Thanks to the abundance of material it was possible to obtain 

 a large number of nuclei in which the nuclear plate was clearly visible. 

 The nucleus and chromsomes are very small, but during the phase of the 

 nuclear plate the chromosomes are far enough apart to be counted easily. 



Also, the size of the nucleus has been determined during the phase 

 of " synapsis" when the nuclear content gathers itself together at one side. 

 The researches of other workers have shown that the difference in the size 

 of the nuclei of different plants is most evident in the sexual cells during 

 this phase of synapsis, and also that the size of the nucleus may serve as 

 a means of morphological distinction between types that are closely related 

 systematically. 



From the data obtained it is concluded that : 



(i) The number of chromosomes in the somatic cells of A. majiis, 

 A. latifoliiim and A. tortuosum is the same, i. e. 18. 



