iqh] current literature 99 



Development of fern prothallia. — Working under Klebs, Isaburo-Nagai 26 

 gives further evidence, through an investigation of the physiology of fern 

 prothallia, in support of the idea that the course of development in plants 

 is largely dependent upon and influenced by external factors. The author 

 divides his work into four parts, dealing respectively with the germination of 

 the spore, the development of the prothallium, the production of rhizoids and 

 sex organs, and the formation of adventitious branches. 



The paper gives an exhaustive summary of previous investigations dealing 

 with the prothallium in ferns, and describes also a considerable amount of 

 original investigation carried out with a view to ascertaining the effect of 

 external conditions upon the qualitative and quantitative courses of develop- 

 ment of the gametophyte. By far the most interesting and significant feature 

 of the work is the extent to which the investigator is able to induce or inhibit 

 the formation of sex organs, the appearance of apogamy, and finally of adven- 

 tive shoots. Interesting, too, but possibly of less significance, are the changes 

 of form which he seems able to produce in the thallus. 



He finds, for instance, that where the nutrient solutions on which the 

 spores are germinated are poor in potassium, magnesium, and calcium, both 

 antheridia and archegonia may be formed; on the other hand, while antheridia 

 may be formed quite readily in a solution containing little or no nitrogen, the 

 production of archegonia cannot take place. In other forms, where germina- 

 tion and vegetative growth go on in darkness as in light with equal facility, no 

 antheridia are set in the former instance. The experiments further point 

 to a direct connection between the concentration of the nutrient solution and 

 the production of sex organs, since under scant illumination archegonia are 

 not developed in the weaker concentrations. Still other results indicate that 

 if the prothallium be kept under conditions favoring vegetative growth, sex 

 organs will not appear; and the author concludes from this that sex organs 

 are produced only on prothallia whose vegetative growth has been hampered 

 (ameristic prothallia). 



In this connection, Isaburo-Nagai brings up the question of the distribu- 

 tion of sex organs, pointing out the fact that whereas the antheridia are gener- 

 ally scattered over the entire prothallial surface, the archegonia are restricted 

 to the meristematic region around the notch. His explanation of this situa- 

 tion, however, is far from satisfactory, and will need considerable experimental 

 backing before it is given general acceptance. Briefly, the author first remarks 

 the difference between the egg and the sperm, in that the latter is poor in 

 albumen, with which the former is abundantly supplied; secondly, that the 

 cells of the apical region of the prothallium are also rich in albumen; and 

 thirdly, that the archegonia are probably restricted to this apical region 

 because they derive their excessive protein supply from the meristematic cells. 



106:281-330. figs. 18. 1914. 



Untersuchungen iiber Farnprothallien. Flora 



