1906] COOK—CUBAN NYMPHAEACEAE 379 
The nucleus next to the embryo divides repeatedly, thus forming the 
endosperm which will be described later. The nucleus in the anti- 
podal end acts slightly differently in the different species and will 
hereafter be designated the nucleus of the nucellar tube. 
In Nymphaea advena a long tube-like extension of the sac is 
now formed through the nucellus, beginning with the antipodal end 
of the sac and extending to the chalazal end of the ovule. The very 
large and conspicuous daughter nucleus of the antipodal end, formed 
by the division of the endosperm nucleus, enters this tube, which 
will be called the nucellar tube, and travels to the chalazal end of the 
ovule, where it undergoes disintegration (figs. 8, 12, 13, 14). When 
the embryo is in the two-celled stage, the tube and nucleus have 
traveled about two-thirds the length of the ovule (figs. 8, 12); and 
when the embryo has reached the quadrant or octant stage, the tube 
is complete (figs. 13a, 13b). In one case only (fig. 13) the tube 
nucleus had divided. After this time it disintegrates (jig. 14). In 
its early development the tube is filled with protoplasm which to all 
appearances is traveling towards the embryo sac. This is exactly 
the condition observed by me in Nymphaea advena and Castalia 
odorata and described in my first paper (7). 
In Castalia ampla (fig. 20) the nucellar tube is a short thick sac 
which is separated from the embryo sac by a constriction and by a 
thin wall, and which contains a very large nucleus and a large amount 
of protoplasm, As the embryo increases in size, the embryo sac 
enlarges, encroaching upon this nucellar tube sac and absorbing its 
contents (fig. 21), The formation of this tube sac is very similar 
to that described by JoHNson (12) for Sawrurus cernuus, except 
that in that species the tube ‘sac is relatively larger and persists in 
the mature seed, 
In Castalia pubescens the nucellar tube is much slower in develop- 
ment, much less conspicuous, and apparently of much less importance 
than in any of the other species studied. Extending from the antip- 
odal end of the sac to the chalazal end of the ovule is a great mass 
of elongated cells (fig. 24) which are much richer in protoplasmic 
contents than the other cells of the nucleus. The greater part of this 
mass of cells disintegrates slowly and thus is formed a small tube 
reaching usually not more than one-half the length of the ovule 
