336 SUMMARY OF CURRENT RESEARCHES RELATING TO 



fcers which they exhibit. After reference to and comment upon the 

 important work upon this subject done by Winkler and Baur, the author 

 describes such a plant which he has had in his possession for some time, 

 and draws conclusions from his observations. The plant in question is 

 a graft-hybrid of an orange and a citron, and the characters of both 

 plants are clearly distinguishable both externally in the foliage, flowers 

 and fruit, and also in the internal structure of vegetative and reproduc- 

 tive tissue. Reference is also made to the graft-hybrid of Laburnum 

 vulgare and L. Ail ami. The author has tested the theory enunciated 

 by Beijerinck as to the presence of a specific substance capable of trans- 

 mission from cell to cell, to which the special characters owe their origin. 

 There appears to be nothing to confirm this theory, but the present 

 work tends to show that the specific individual characters are due to the 

 presence of different nuclei. As in bastards the mingling of characters 

 is due to the mingling of the parental chromosomes in the same nucleus, 

 so in graft-hybrids the distinct characters exhibited by different parts 

 of the plant are due to the presence of different nuclei. According to 

 the character of the nuclei in each individual part of the plant, so will 

 that part develop. Nothing can as yet be stated as to the reason for 

 the varied distribution of the nuclei, but the results of it are most appa- 

 rent in the generative organs, where it may cause sterility, but on the 

 other hand may be associated with normal fertility. 



Hybridisation in Mirabilis* — D. C. E. Marryat has experimented 

 with hybrids of Mirabilis Jala/pa with special reference to the flower- 

 coloration. Three colour varieties were used, all of which bred true. 

 The most important results of the experiments appear to be the following : 

 A white form, when crossed by yellow, gave a pale-yellow hybrid, thus 

 confirming a prediction made by Correns. This same white form when 

 crossed by crimson had offspring coloured crimson, magenta, orange-red, 

 yellow, or white ; this series of colour is the same as that obtained when 

 any of the other white forms was crossed by yellow, but there is no 

 ; ' flaking " as in the latter case. This same white when crossed by other 

 whites produced coloured forms. Heterozygous forms are always dis- 

 tinct in colour from homozygous forms, and therefore the scheme 

 -n^gested by Correns needs considerable ruudifieation. It does not yet 

 seem possible to regard " flaking " as represented by Mendelian factors. 



Inheritance of Flower-colour in Antirrhinum majus.f — M. AVhel- 

 dale has made further investigations as to the flower-colour in Antir- 

 rhinum, and finds her previous conclusions in respect to Mendelian factors 

 amply verified. The final results are briefly as follows. The flowers of 

 the wild plant are originally magenta, the colour being due to an antho- 

 cvanic pigment accompanied by ferments. The pigment itself is an 

 oxidation product. Where the necessary oxydase is not formed the 

 pigment is not produced, and ivory-white flowers are the result. By 

 the loss of another constituent, probably a ferment, yellow is produced. 

 The yellow pigment when oxidised produces crimson. Complete absence 

 of chromogen results in pure white flowers. The absence or presence 

 locally of either oxydase or ferment causes local variation in colour. 



* Roy. Soc. Rep. Evol. Comm., v. (1909) pp. 32-50 (2 pis.). 

 t Tom. cit., pp. 1-25. 



