Allen—Spermatogenesis and Apogamy in Ferns. 
35 
mum. Not infrequently, twenty-eight spores are found, indi¬ 
cating the abortion at some stage in the development, of one of 
the spore mother cells. There are sometimes even fewer. 
Cases in which one pair of spore mother cells fail to fuse may 
account for some of the cases in which twenty-eight spores have 
been found in a sporange. There is no evidence that the un¬ 
paired cells can undergo a, double division to form spores. 
Cases of incomplete fusion such as those already described may 
also explain reductions of the final spore number. 
The question as to the number of chromosomes in the nuclei 
of the sporophyte of apogamous ferns as contrasted with those 
in which normal fertilization occurs, has attracted much atten¬ 
tion in recent years, and in the light of the facts as to the 
fusion of the spore mother cells above described it becomes 
especially important for Aspidium falcatum. In my sections 
of prothallia, I have not found division figures common. Fig¬ 
ure twenty-six shows a characteristic division figure in the 
young antheridial sac as described above. It represents an 
early anaphase in the first division. About one-third of the 
total number of chromosomes are represented in the drawing. 
The chromosome number is so large and the chromosomes are 
so massed together that a single counting cannot be depended 
upon to give trustworthy results. The difficulties in the way 
of arriving at an exact determination of the number of chromo¬ 
somes in any particular division are very great. I have fol¬ 
lowed the plan of making at least three separate counts for 
each division figure. The three numbers so obtained varied 
from each other within a range of five or six. It is an average 
of the three counts in each case which I have taken as represent¬ 
ing the nearest possible approximation to the actual number. 
The two chromosome groups in the diaster of a vegetative 
division in the prothallium when counted in this manner showed 
respectively 62 and 61 daughter chromosomes. The three 
countings of the first figure gave 61, 62, and 63; for the second 
63, 60, 60. Four equatorial plates from an antheridial sac 
counted in the same way showed respectively 61, 63, 58 and 
60 chromosomes. The three countings from which in each case 
