482 THE AMERICAN NATURALIST. [VOL. XXXIX. 



of time and may occupy even weeks or months. During this 

 interval the spore mother-ceils increase to many times the size 

 of the archesporial cells from which they were derived. There 

 is an immense accumulation of protoplasmic material and a cor- 

 responding increase in the size of the nucleus and its chromatin 

 content. The growth may be continued in the spores after the 

 mitoses of sporogenesis, as is characteristically illustrated in the 

 great increase in the size of the megaspores in the pteridophytes 

 and certain embryo-sacs. The most striking nuclear activity of 

 the growth period preceding the mitoses is synapsis. This term 

 is applied to a very characteristic gathering of the chromatin and 

 linin material in a compact tangle or ball at one side of the 

 nucleus and usually near the nucleolus. Nuclei are sometimes 

 in a state of synapsis for several days or perhaps weeks as is 

 shown by the frequency of the stage in sporogenesis. Thus 

 during the entire period of sporogenesis in Anthoceros from the 

 inception of the spore mother-cell to the final differentiation of 

 the spores (which must take many days) the period of synapsis 

 occupies from one eighth to one sixth of the entire time (Davis, 

 '99, p. 104). Synapsis has proved to be a very difficult subject 

 for study and few investigators have made detailed observations 

 upon its events. Some have claimed that synapsis is an artifact 

 due either to poor fixation or to a particularly sensitive condi- 

 tion of the cell nucleus by which the chromatin was especially 

 susceptible to shrinkage but it seems certain now that the 

 phenomenon is entirely normal. Miss Sargant ('97, -p. 195) has 

 observed synapsis in the living pollen mother-cell of Lilinm 

 mart agon. Anthoceros presents a particularly favorable subject 

 for the study of the effects of fixing fluids on spore mother-cells 

 because one may present all stages in the same sporophyte to 

 identical conditions. In a series of experiments on this form 

 (Davis, '99, p. 97) with a number of standard fixing fluids I have 

 always found synapsis at exactly the same period in sporogenesis 

 and at no other time in the process. True synapsis, character- 

 istic of reduction phenomena must be carefully distinguished 

 from other somewhat contracted conditions of the chromatin 

 which are cccasionally found in cells. Thus Miyake {Annals of 

 Bot., vol. 17, p. 358, 1903) noted the resemblance to synapsis 



