120 Scott and Mas ten . — The Structure of Trigonocarpus. 
them, and that they generally correspond in position with the longitudinal 
vascular strands to be described later. 
The structure of the nucellus, as seen in the best-preserved sections, 
is shown in PL XII, Fig. 15, and PI. XIV, Figs. 29-31. Externally, 
there is a single layer of cells forming an epidermal layer, n.e ., readily 
distinguishable from the underlying tissue. These cells are usually filled 
with dark contents similar in appearance to those of the hypodermal cells 
of the sarcotesta. In longitudinal sections (PL XII, Fig. 15) these cells, 
n.e., are usually somewhat elongated in the longitudinal direction, and 
have an average length of about »o8 mm., but vary considerably among 
themselves in this respect. Fig. 15 is magnified about forty times, and 
is taken from a portion of the nucellus which is quite low down in the seed, 
but similar cells can be seen around the nucellus in most parts of this 
longitudinal section, so that it is clear that they extend from the chalazal 
attachment upwards. The nucellar epidermis closely resembles that of 
Stephanospermum , described and figured by Prof. Oliver L 
PL XIV, Fig. 29, represents a portion of the nucellus from a section 
of Trigonocarpus Parkinsoni lent by Prof. Oliver, and is magnified about 
560 times. The nucellar epidermis is shown at n.e., and, as is commonly 
the case, the cuticle of the cells, c.e ., is separated. In this section the 
epidermal cells are empty, but usually they are filled with the characteristic 
dark contents. 
PL XIV, Figs. 30 and 31, are made from the same section, a good trans- 
verse one lent by the Manchester Museum. The magnification is about 160 
times. In Fig. 30 the nucellar epidermis, n.e., is poorly preserved, and only 
the cuticle is clearly seen. In Fig. 3 1 the cuticle of the nucellar epidermis 
is shown at e ., and the contracted contents of the cells at c.e. In many 
sections the nucellar epidermis is represented only by its cuticle, which 
persists as a fine line separated by a space from the rest of the nucellus. 
Within the epidermis good sections show a tissue consisting of thin- 
walled flattened cells (PL XIV, Fig. 31, it). As shown in Fig. 31, the cells 
of this intermediate layer are flattened in the radial direction, and as far as 
can be made out from the longitudinal sections they are elongated vertically. 
The corresponding cells shown in PL XIV, Fig. 30, i., are less flattened, 
possibly because they are opposite to one of the outwardly directed processes 
already mentioned. 
The innermost layer of the nucellus may be distinguished as the 
tracheal zone, consisting as it does mainly of delicate tracheides with spiral 
or scalariform thickenings (PI. XIV, Fig. 31, /.). The vascular bundle 
which comes in at the chalaza spreads out into what is apparently a con- 
tinuous mantle of tracheides in the lower part of the seed. In some of the 
transverse sections across the lower part of the body of the seed the 
1 Oliver (’04) (1), PI. 43, Fig. 21. 
