Dicotyledon—Ca It ha palustris . 529 
last year, quite prepared to extend my researches to other 
plants if L. Martagon proved fruitful speedily. The material 
must have been extremely rich in this stage, and very well 
fixed, for both hand sections and microtome series yielded 
very good instances at once. 
As the matter seemed fairly well established for typical 
Monocotyledons, it became desirable to see if the second fertili¬ 
zation took place in Dicotyledons also. At Professor Farmers 
suggestion I sectioned Caltha palustris among other plants, 
and this seemed to be a favourable object for study, although 
too old. I therefore went out in search of fresh material, and 
obtained it from Hackbridge, where it grew very abundantly. 
The ovaries were pickled on one or two bright mornings 
(11.30 and 13.30) at the end of May, some in absolute alcohol 
and 35% acetic acid, and some in strong Flemming’s fixative. 
Those chosen were mostly from fresh flowers, but of different 
ages, as far as one could judge from their appearance. I know 
now, since carefully marking flowers of Caltha this spring, 
that they remain open for at least seven days, and this 
material must therefore have included ovaries of very different 
ages. Microtome sections were cut, for the most part, from 
the Flemming material, and hand sections from that fixed 
in absolute ale. and 25 °/ 0 acetic acid, but curiously enough the 
most interesting preparations were obtained from microtome 
sections of ovaries from the latter material, so that these 
are not so well preserved as many of the less important 
stages. Hand sections were stained in Methyl Green and 
Fuchsin, but the microtome sections were stained with 
Flemming’s Triple Stain or Ehrlich’s Haematoxylin. 
The relatively large size of the oval-shaped embryo-sac 
and small size of the nuclei renders it difficult, and perhaps 
almost impossible, to obtain preparations in which the proto¬ 
plasm is not somewhat strained. In some of the younger 
stages, in which the polar nuclei are only just in contact 
with one another, the sac is much smaller, and well filled 
with protoplasm ; and in these the preservation is quite good. 
Later, the embryo-sac enlarges considerably, and the vacuoles 
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