EMBRYOLOGY OF THE AMENTIFERÆ. 415 
CORYLUS AVELLANA, Linn. (Pl. LXX. figs. 39-43 ; Pl. LXXI. figs. 44-47.) 
Tn this genus we find much that is new and of interest to the embryologist. Although 
the sporogenous tissue is based on the coaxial system, and the strands are particularly 
clearly marked out in the tapetal region, there is less regularity in the region immediately 
above the pedicel. The cells are there smaller and more granular, and several early show 
signs of further development. Тһе sections given in figs. 41, 42, 43 were prepared in 
June and July 1892 from the fresh material. In fig. 42 one embryo-sac had separated 
from the section, and its position is indicated only by a gap in the nucellar tissue (p.e.s.). 
Later on, one of these embryo-saes sends out a protuberance which passes down towards 
the base of the nucellus. Figs. 46 and 47 represent a cæcum with a pollen-tube abutting 
upon it. Figs. 44 and 45 also represent a pollen-tube—in sifu—passing up the nucellus 
from the chalaza. The cecum attains considerable length only when the embryo begins 
to develop. In this, Corylus offers a striking contrast to Carpinus. 
On two occasions I have found two fully-developed embryo-sacs, and in these cases 
they elongated side by side. The egg-cell covers itself with a cellulose wall and becomes 
attached to the apical part of the wall of the sac. The synergidee never become so 
large and conspicuous as those of the Cupuliferz. 
CanprNUs BETULUs, Linn. (Pl LXXI. figs. 48-50; РІ. LXXII. figs. 51-60.) 
There is much that is similar to Corylus in the early stages of Carpinus. Fig. 48 
shows the area of the sporogenous tissue and pedicel as marked out in a longitudinal 
section. The embryo-sacs arise chiefly from the central strand, and two or more take on 
a full development and send long ceca down to the base of the nucellus. In fig. 49 
only one of these is indicated, fig. 54 shows two, and fig. 53 four; but it is rare to find 
the cæca quite in the same plane. These cæca are best seen in a comparatively thick 
section of the nucellus, which is composed of remarkably large and transparent cells in 
Carpinus. Such a section sometimes reveals a nucellus riddled by these tubes, which 
necessarily come into close contact at the narrow base of the nucellus. These tubes 
reach their full length before any endospermic nuclei are formed, and the definitive 
srotoplasm which reaches from the apex to the 
nucleus is conspicuous in the cordon of proto j 
base of the embryo-sac. It is by means of these dense continuous tongues of protoplasm 
that we can best trace the course of the cæca in Carpinus, and. it is along these that I 
have on several occasions traced a pollen-tube, which, after entering the base of the 
cæcum, makes its way to the egg-cell. Fig. 50 shows one still persisting after 
fertilization has occurred. 
The Pollen-tube. 
This subject may be advantageously treated under the three headings of 
Resting Stage, 
Chalazal Route, | 
Branching of the Tube. 
_ Resting Stage—In Gochel’s ‘Outlines of Classification and Special Morphology,’ 1 
