MICHIGAN ACADEMY OF SCIENCE. 75 



case of Aspidkini falcatum, oue of tlie fcni.s. For several decades 

 it had been known that the sporophyte developed from the prolifer- 

 ation of the cells of the gametophyte, not from a fertilized egg. 

 The gametophyte produces antherids with normal sperms but the 

 archegones degenerate before the eggs reach maturity so that the 

 latter are never fertilized and in fact never function at all. On 

 the sporophyte are produced typical sporangia within which spores 

 are produced which give rise to the new gametophyte. It has been 

 known for some years that spore production Avithin the fern 

 sporangium is typically brought about by the formation of four 

 spores each in usually sixteen spore mother cells, the nuclear di- 

 visions being in the nature of reduction divisions. Manifestly re- 

 duction divisions cannot continue to occur at each generation un- 

 less there is a nuclear union somewhere, and this is entirely lack- 

 ing in the gametophyte. 



Miss R. F. Allen, accordingly took up this point and investigated 

 the development of the sperms and of the sporangia of the gameto- 

 phyte and sporophyte respectively. She determined the chromo- 

 some number in the gametophyte to be between 60 and 05,. with 

 perfectly normal development of the sperms. The sporophyte also 

 had the same chromosome number, a confirmation of the previous 

 observations in which no cell union had been observed. In the 

 sporangia there appeared sixteen cells exactly like the sixteen 

 spore mother cells. of normal fern. These, however, united by pairs 

 with complete fusion of both cells and nuclei, thus producing eight 

 cells with diploid nuclei. Each now acted like a normal spore 

 mother cell and its nucleus underwent reduction division and 

 four spores were formed in each cell ; thirty-two for the sporangium 

 instead of sixty-four as for normal ferns. 



It is manifestly entijrely improper to call the leafy plant on which 

 the sporangia were borne a gametophyte because of retaining the 

 haploid number of chromosomes in its nuclei. If that is done then 

 the sporophyte is only one-celled, for at only one stage is the 

 nucleus diploid, i. e., just after the fusion of the two spore mother 

 cells. 



Miss Allen calls attention to cases where the gametophyte retains 

 the diploid number of chromosomes, as in some apogamous flower- 

 ing plants, e. g., Antennaria, Hieracium, Thalictrum, in which the 

 embryo sac arises without a preceding reduction division although 

 this may be present in pollen production. In such embryo sacs 

 the egg develops apogamously. In certain cultivated varieties of 

 ferns fertilization and development are normal; in closely related 



