Mr. GnirrITH on the Ambrosinia ciliata of Roxburgh. 269 
occurs until after impregnation and after the withering of the spatha. The 
central portion of the nucleus is then much more transparent, and is evidently 
excavated. The shape of the cavity is clavate, the narrow extremity: being 
contiguous to the hilum, the broader pointing to the apex of the nucleus. 
The opening in the integument is still conspicuous. The next step that I 
examined presented a considerable enlargement of the integument or testa, 
which had become cellular, and its cavity had assumed an irregular form. The 
foramen was indistinct. The nucleus had become much firmer, and its cavity 
much enlarged and considerably altered in Shape. This cavity, which is due 
to excavation, as I believe is most commonly, perhaps invariably the case, 
extended upwards to within a very short distance of the extreme apex of the 
nucleus, which was apiculate; and downwards towards the hilum, the dia- 
meter being greater at its base than elsewhere. The lower portion was occu- 
pied by cellular tissue assuming the form of a sac and quite free from adhesion 
inferiorly. The upper third of the excavation was occupied by an oblong cel- 
lular body, the apex of which is conical. This is the young embryo; it is at 
the period mentioned entirely cellular, and its attachment to the nucleus is, 
if any, extremely slight. 
When rather more advanced, the embryo is still entirely inclosed within 
the nucleus. It is subclavate, the conical, originally rectilinear apex has 
become somewhat oblique, and on one side of what may be called the head of 
the embryo, a depressed areola is visible. The next change. presents an 
enlargement upwards of the excavation, which is now continued through the 
apex of the nucleus. At the same time its base has become enlarged and 
roundish. At this period the nucleus with its cavity resembles, not very 
 inaptly, a Florence flask. The conical and rather oblique apex of the embryo 
now projects through the perforated apex of the nucleus, the inclosed part 
being firmly embraced by the zeck of the nucleus, the tissue of which has 
become more and more callous or indurated. The next important change 
embryo, and in the production of minute, oblong, obtuse, cellular bodies from 
the margins of the depressed areola. These bodies are the rudiments of the 
outer processes of the plumula. A little later, these marginal papillae will be 
found enlarged, and at the same time additional ones will be seen d 
2N2 
eveloped 
