468 BOTANICAL GAZETTE [june 



f 



NOTES FOR STUDENTS 



Inheritance of sex. — Correns 3 has continued his studies on gynodioecious 

 plants in order to discover what determines the sex of the flowers on the gynomo- 

 noecious individuals, and the sex of the two classes of individuals belonging to 

 such species. He finds that the curve of frequency of hermaphrodite flowers in 

 Satureia hortensis, instead of presenting two modes, as previously reported by 

 him, one in the mid-season and one at the end of the season, has only a mid-season 

 mode. The mode which appeared at the end of the season w r as due to the repeated 

 counting of flowers which remained open more than one day. 



During the middle of the season no flowers open on the second day, but late in 

 the season the petals seem to be more resistant, and climatic conditions are less 

 severe, so that the same flowers were unwittingly counted several times. When 

 each flower is marked as it is counted, it is found that the proportion of hermaphro- 

 dite flowers continues to fall till the end of the season. 



He also tested the effect of environmental conditions upon the percentage 

 of hermaphrodite and female flowers produced on plants of Satureia from day to 

 day, and noted the position occupied by each kind of flower on the plant. The 

 results show that poor nutrition, whether the result of poor soil, insufficient illu- 

 mination, or disadvantageous position on the plant, lessens the proportion of 

 hermaphrodite flowers, and under the combined influence of both poor soil and 

 poor light, only 13 per cent, of hermaphrodite flowers were produced as compared 

 with 79 per cent, produced under normal conditions of culture. However, the 

 general features of the curve of frequency of the hermaphrodite flowers remain 

 the same. With high nourishment the curve for the hermaphrodite flowers falls 

 much more gradually toward the end of the season, though during the early part 

 of the season it is not essentially modified. 



It was found that different strains of Satureia show marked differences in the 

 actual percentage of hermaphrodite and female flowers, but that in. each case the 

 general features of the curve of frequency are the same. The conclusion is 

 reached that whether hermaphrodite or female flowers are to be produced by a 

 gynodioecious individual is dependent upon nourishment in its widest sense. 

 The same general results may be demonstrated in Geranium, Silene inflata and 

 5. dichotoma, Plantago lanceolata, Scabiosa, Knautia, and Echium. 



Darwin had observed that a single hermaphrodite plant of Satureia hortensis 

 was "rather larger" than the female plants of the same species, and in an earlier 

 paper Correns had apparently substantiated this observation, without realizing 

 the possibility that some of the plants classed as female might be hermaphrodite 

 plants, rendered apparently female by poor nutrition. He undertook to determine 

 the relative weights of these two classes of plants with a more careful analysis of 

 the material. The results show that there is no difference in weight between the 



3 Correns, C, Weitere Untersuchungen uber die Geschlechtsformen polygamer 



Blutenpflanzen und ihre Beeinflussbarkeit. Jahrb. Wiss. Bot. 45:661-700. figs. «• 

 1908. 



