No. 503] XOTES AND LITERATURE 



743 



PLANT CYTOLOGY 



Apogamy in the Ferns. — It has long been known that the arche- 

 gonia in a number of ferns are not functional and that in these 

 forms the sporophyte generations arise as vegetative outgrowths 

 from the gametophytes. This suppression of sexuality with the 

 development of the succeeding generation asexually is termed 

 apogamy. Only recently, however, have there been any cytolog- 

 ical investigations of the phenomenon. 



Farmer and Digby 1 were the first to study the nuclear be- 

 havior throughout critical phases in the life history of apogam- 

 ous ferns. The results, based on forms of Lastrea, Athyrium, 

 and Seolopendrmm, led these authors to describe three con- 

 ditions. 



1. The process of sporogenesis is omitted from the life cycle 

 in three varieties of Athyrium Filix-famina and in a form of 

 Scolopendrium giving the condition of apospory known for a 

 number of ferns. The prothallia arise directly from abortive 

 sporangia or from pinna' ; the sporophytes develop apogamously 

 from the prothallia or from unfertilized eggs; and the approxi- 

 mate number of chromosomes is retained throughout the life 

 cycle. This type of life history brings apogamy into close asso- 

 ciation with apospory. The omission of the process of chromo- 

 some reduction, characteristic of sporogenesis. gives the gameto- 

 phytes the sporophytie number of chromosomes i 2x). Apogamy 

 seems to be a natural consequence, for gametes would not be 

 expected to function under such conditions since they would 

 double the number of chromosomes with each nuclear fusion 



mitoses are omitted in the ovule and the nuclei of the embryo 

 sacs contain the sporophyte number of chromosomes, the embryo 

 developing from tin fertilize* I eggs or even from synergids. The 



