470 SUMMARY OF CURRENT RESEARCHES RELATING TO 



sequence of sporangia, combined with its primitive characters and its 

 probable affinity to the Ptcrideae, shows that a great phylum of Mixtae 

 has probably been derived directly from the Simplices. 



Apogamy in Pteris droogmantiana.*— E. L. Stephens and M. G. 

 Sykes publish a preliminary note on apogamy in Pteris droogmantiana. 

 They have made a cytological investigation of its prothallus. In the 

 young prothallus binucleate cells are common, the extra nucleus not being 

 due to migration but to nuclear division. These nuclear pairs mostly 

 fuse eventually, the resultant nuclei being very large and often lobed 

 at first. 



Apogamy, Hybridisation, and Heredity in certain Ferns.|— A. 

 Heilbron publishes a paper divided into three parts, namely, an account 

 of Cystopteris fragilis f . potyapogama (a new form) ; the hybrid nature 

 of Asplmium germanicum ; the conditions of heredity in cultivated garden 

 ferns. He sums up his results as follows :-— 1 . Cystopteris fragilis f . poly- 

 apogama produces prothallia which have the power of developing sporo- 

 phytes from the egg-cells apogamously one after the other, or exceptionally 

 even alongside one another. 2. The question whether Asplenium ger- 

 manicum is a hybrid of two recent forms is not yet cleared up, although 

 a crossing of A.septentrionale 9 and A. Ruta-muraria <£ produced a plant 

 which stands nearer to A. germanicum than any other hitherto known 

 form. ?>. Apogamy has been found in certain ferns in which it was 

 previously unknown. Imported British forms of Athyrmm filix-femina 

 are partly hereditary and partly reversionary forms. Artificial treatment 

 failed to elicit forking of the frond, and spontaneous forking is not 

 inherited. 



Fertilisation and Hybridisation in Ferns.}— W. D. Hoyt discusses 

 the physiological aspects of fertilisation and hybridisation in ferns, and 

 gives an account of some observations made upon the movements and 

 reactions of sperms. He is very sceptical as to the value of the " hybrid " 

 ferns described in recent papers, and suggests that their peculiarity of 

 form may be due to the effect of the particular soil on which they grew, 

 or to other ecological conditions. He sums up his laboratory observa- 

 tions as follows :— 1. Entrance of sperms into archegonia was obtained 

 in every combination of species tried. 2. When egg and sperm were of 

 the same species, entrance into 97 archegonia, as shown by sections, 

 resulted in 37 fusions ; but when egg and sperm were of different species, 

 entrance into 129 archegonia failed to give a single fusion. A similar 

 result was obtained by replanting prothalli on soil after entrance had 

 occurred. ?,. The results obtained, while not disproving the existence 

 of fern hybrids, indicate that conclusions based on the structure of the 

 sporophyte should not be accepted without additional experimental evi- 

 dence, and show that not every combination of egg and sperm can result 

 in a fusion. 4. Sperms of one species were observed within the arche- 

 gonia of another species boring against the egg. The failure of such 

 sperms to enter the egg does not seem to be due to any failure of the 



* Ami. Bot., xxiv. (1910) p. 487. 



t Flora, n.s., i. (1910) pp. 1-42 (43 figs.). 



X Bot. Gaz., xlix. (1910) pp. 340-70 (figs.). 



