No. 463-] STUDIES ON PLANT CELL VI. 483 



of an accumulation of granular material in the nucleus of the 

 central cell of Picea and other cases might be cited which super- 

 ficially resemble synapsis but have no fundamental relation to 

 this peculiar nuclear activity. 



Evidence is steadily accumulating that synapsis is a very 

 important period of sporogenesis. Some authors hold, as will 

 be described presently, that it is the time when paternal and 

 maternal chromosomes, which have remained separate through- 

 out the sporophyte generation, become associated in pairs to 

 give the reduced number of the gametophyte. This conclusion 

 makes synapsis the actual period of chromosome reduction and 

 the two succeeding mitoses become merely distributing divisions 

 of the newly formed chromosomes. Montgomery (: 01) first 

 suggested for animals that synapsis involved a union of maternal 

 and paternal chromosomes in pairs. Other views, however, 

 regard the reduction of the chromosomes as merely the tempo- 

 rary union of paternal and maternal elements, end to end, to 

 form a bivalent chromosome characteristic of the first or hetero- 

 typic mitosis. According to this view the bivalent chromosomes 

 divide transversely so that the halves are distributed as whole 

 chromosomes in the first mitosis. 



Two very important papers on reduction phenomena have 

 appeared this year (1905) both of which were preceded by pre- 

 liminary publications, that of Farmer and Moore (: 03) and 

 Allen (:O4). These two accounts best represent the attitude of 

 the opposing schools and will be made the chief texts of our 

 treatment. The fundamental points of difference concern the 

 events of synapsis and the heterotypic mitosis while there is 

 complete agreement in the general interpretation of the homo- 

 typic mitosis. All authors have reached essentially the same 

 conclusions as regards the purpose and final results of the 

 reduction divisions but the details of the processes of synapsis and 

 the prophaseof the heterotypic mitosis are described in radically 

 different ways by various investigators. However, as has been 

 stated, the views fall into two groups or schools, one led by 

 Farmer and Moore with whom Strasburger's recent paper, 

 <l Ueber Reduktionsteilung " (1.04) expresses essential agree- 

 ment. The other school includes Allen, Rosenberg, and the 



