NOTES AND ABSTRACTS. 



635 



place in the bud. If, however, cross-poUination is effected imme- 

 diately on the opening of the bud, the foreign pollen grows more rapidly 

 than the grains from the same flower, . and cross-fertilization is 

 brought about. If no such cross-pollination takes pl,ace, the pollen 

 from, the same flower (which reached the stigma during the bud stage) 

 continues its growth and effects self-fertilization. A number of 

 experiments are quoted to show the quicker growth of the foreign 

 pollen than the self -pollen. This is an interesting adaption by which 

 self-fertilization is assured if cross-pollination fails to take place. 



A number of experiments were carried out upon the life and 

 germination of the pollen-grains of coffee. They germinate in water. 

 They germinate particularly well in cane-sugar solutions of 20 per 

 cent. The pollen-grains were also grown on solid media, such as 

 agar-agar. The effect of various carbohydrates (grape sugar, milk 

 sugar, arabinose) upon the growth of the pollen-tube was tested. 

 Malic acid was found to have no accelerating effect upon the growth 

 of these pollen-tubes. The length of life of the pollen-grain under 

 different external conditions was studied. The moisture of the 

 atmosphere was found to exert a very considerable influence on the 

 length of life of the pollen-grains. Thus the pollen-grains of Coffea 

 liberica only remained capable of geraiination for two days in an 

 atmosphere with a vapour tension of 90 per cent., whilst with a 

 vapour tension of 30 per cent, they retained their vitality for seven 

 days, and in air dried over concentrated sulphuric acid they remained 

 unharmed for eight days. The partial sterility of some varieties of 

 coffee is a well-known phenomenon to planters, and the present 

 author describes its appearance and the cytological processes which 

 determine it. 



The sterile blooms known by the Dutch name of " sterretjes " are 

 described in the next section of the work. They are most common in 

 G. arahica, less common in C, liberica, and very rare in C. Laurentii, 

 C. Uganda, and G. quillon. 



In these flowers the calyx is either entirely absent or reduced to a 

 minute rudiment ; the corolla is also very much reduced ; and the 

 petals are fleshy in substance instead of thin as in the normal flowers. 

 The stamens are also modified in these " sterretjes " blooms. 



The cytology of the sexual apparatus of these blooms is described. 



The author concludes that these flowers are ordinary blooms which 

 from some cause or other have become arrested at an early stage of 

 their development. Experiments were made by the author to deter- 

 mine, if possible, the causes producing the sterility of the blooms. 

 The effects of light and of soil-moisture, separately or combined, were 

 especially studied. — R. B. 



ColouP-ChangeS in Flowers. By H. Fitting (Zeitschr. f. Bot., 

 Bd. iv. pp. 81-105 ; 1912). — The normally blue flowers of Erodium 

 gruimun and E. ciconium become rose-red when heated, and at a high 

 temperature almost colourless. On cooling, the changes are reversed, 



