455 
Sexual Nuclei in Lilium Martagon. 
the chromosomes accurately and found twenty-four of them. 
In all others difficulties of observation prevented me from 
determining the number with absolute certainty. The 
question always lay between twenty-three and twenty- four, 
or between twenty-four and twenty-five. 
A median hypodermal cell becomes larger than its fellows 
some time before the appearance of either integument. The 
nucleus of this larger cell usually remains for some time in 
the resting-stage and becomes the embryo-sac nucleus without 
further change, but not infrequently it divides once again. 
This accounts for the occasional appearance of twin embryo- 
sacs which is not infrequent in very young stages. In other 
cases two nuclei are found in the same embryo-sac long 
before the regular period for division, and I have seen several 
instances of twin spindles. One preparation shows a double 
embryo-sac with four spindles in it which is evidently a case 
of a twin second division. These anomalous cases are not 
numerous enough however to account for all the instances 
in which I have found a nuclear division taking place within 
an enlarged hypodermal cell. Probably the rule is that one 
of the daughter-cells increases in size at the expense of the 
other and becomes the embryo-sac. The karyokinesis itself 
is of the usual nucellar type. 
The structure of the resting nucleus in the very young 
embryo-sac is precisely similar to that of the nucellar nuclei 
surrounding it. A network of dotted threads is partially 
concealed by the substance I have called amorphous chro- 
matin. There is either a single large nucleolus, or more 
commonly several of different sizes (Figs, io and io a). 
A glance at Table I will show that the nucleus remains in 
the resting state until the pollen mother-cells have completed 
their double division. This probably takes about a fortnight. 
During this time the nucleus increases in size, almost doubling 
its diameter, without materially altering in structure (Fig. 11). 
The threads become thicker and their dots larger, but the 
latter still form a single row (F%. 11 a). Anastomoses seem 
to take place, but may be only apparent. The amorphous 
H h 
