1906] COOK—CUBAN NYMPHAEACEAE 377 
ters into the flowers; that while the genus Castalia has been described 
as having four sepals, C. odorata usually has only three, though some- 
times by an expansion of the receptacle one segment of the second 
cycle is more or less exposed, while in C. tuberosa the displacement is 
normal, This led me to make a similar study of C. pubescens. In 
this species I found that 80 per cent. have the first segment of the 
second cycle exposed, while 20 per cent. have the second segment 
of the second cycle more or less exposed, thus showing five parts. 
SCHAFFNER also.called attention to certain other secondary resem- 
blances, such as number and arrangement of ovules and ovularies, 
between the Nymphaeaceae and well-recognized monocotyledonous 
plants, 
The vascular bundles of all the species referred to in this paper 
were also studied, but gave no facts other than those already well- 
known, the bundles in all cases being of the well-recognized closed 
type and arranged in the stems after the usual manner of this family. 
On account of the large amount of gummy substance surrounding 
the ovules, considerable difficulty was experienced in getting a killing 
fluid to penetrate. This was especially true for Brasenia purpurea 
where the gummy substance was most abundant. Picric-acetic solu- 
tions proved to be the best fixing agents, while chrom-acetic and 
the Flemming’s solutions were unsatisfactory and could be used only 
for the development of the embryo sac and the stamens. 
_THE EMBRYO SAC. 
The formation of the embryo sacs in all genera is very similar, 
and in fact practically the same as described in my first paper (7). 
I will not give a discussion of each, therefore, but will give a general 
outline and present a series of figures illustrating the more important 
points, with special attention to the mature sac and the changes at 
the time of fertilization and immediately following. 
_ The archesporial cell develops from the hypodermis (fig. 72) and 
1s easily recognized. An indefinite number of tapetal cells, usually 
varying from four to eight, are then produced. Three or four mega- 
spores are then formed. The four may be produced either by a 
regular division of the mother cell into four cells; or occasionally 
by the division of the mother cell into three cells, followed by a divi- 
Sion of the middle one (fig. 2). 
