414 MISS M. BENSON—CONTRIBUTIONS TO THE 
interesting to note this resemblance, as in а short paper published March 1898, but 
which I unfortunately overlooked until the middle of May, the writer expressly states, 
“Тп the nucellus there is no axial row of cells, which usually appears distinctly in the 
rest of the Angiosperms ” *. 
Тһе central axis gives rise eventually to the embryo-sae, which is solitary and at no 
time in its development forms a cecum. Тһе contents of the sac are normal, and the 
egg-cell is ready for fertilization at the end of May. In the material gathered in the 
season of 1892, pollination took place during the first week of May and fertilization 
during the first week of June. Тһе nucellus never attains to anything but а very in- 
considerable size, as the whole fruit is adapted for wind-dispersal. Тһе ovules given in 
longitudinal section (figs. 30 and 31)lay at right angles to the axis of the fruit, but 
before an ovule attains its full development it becomes anatropous, and the stylar canal 
is closed by the outgrowth of loose cellular tissue. These organogenetic details being 
common to the other chalazogamic Amentiferee, and deriving their interest for the 
embryologist chiefly from their bearing on the course of the pollen-tube, I will enter 
into them more fully when treating of that subject. 
ALNUS GLUTINOSA, Medic. (РІ. LXIX. figs. 32, 33; РІ. LXX. figs. 34-38.) 
The coaxial system of strands still obtains in the nucellus of 4 Linus. The tapetum 
above the solitary embryo-sac is proportionately longer than in Betula and іп the Cory- 
lacez. The embryo-sac Нез very deep down in the nucellus, and the tapetum, down 
which for a considerable part of its course the pollen-tube travels, has a grumous 
aspect. It is not, perhaps, an improbable conjecture that the cells exert a chemical 
stimulus upon the tube which enables it to arrive at the apex of the sac after a very 
sinuous course. The contents of the embryo-sac are normal (fig. 88), and the antipodals 
resemble those figured by Treub for Myrica rather than those of Castanea, although there 
is no essential difference, and in all cases cellulose walls are conspicuously present. I 
have given a figure of the embryo of Alnus, which is again normal (fig. 37). 
CORYLACEZ. 
In this group we meet with a far more strongly-developed sporogenous tissue than in 
Betula and Alnus, although it much resembles theirs in character. 
In Corylus and Carpinus we find for the first time among the British Amentifere a 
large number of macrospores which continue their development up to the stage of forming 
two or even four nuclei. In those which continue their development the characteristic 
contents of the normal angiospermie embryo-sac are present, but the synergide and 
antipodals are difficult to recognize, except when first formed. The egg-cell is always a 
prominent object in the upper region of the sac, whilst the definitive nucleus, in a well- 
developed caecum of the sac of Carpinus, attains a large size, reminding one of those of 
Castanea. 
* “Zur Embryobildung der Birke,” by S. Nawaschin, in Bull. Acad. Imp. Sci. St. Pétersb. sér. iii. xxxv. no. 3. 
In this paper Mr. Nawaschin records his discovery of the true course of the pollen-tube in Betula. 
