586 Mur rill. — The Development of the A rchegonium 
alone and followed by Orange G. or Bismarck-Brown, were 
useful for comparison in some stages of archegonial develop¬ 
ment and oogenesis. Methyl-Green, Fuchsin, and Orange G. 
were used in the search for centrospheres and some slides 
were covered without staining. After the usual process of 
dehydration with absolute alcohol and clearing with oil of 
cloves, the sections were treated for several minutes with 
Bergamot oil before being covered with balsam. This 
removes foreign particles and ensures the permanence of 
certain stains that are extracted by the oil of cloves: it 
also flows easily and dries quickly. 
The Origin and Development of the Archegonia 
BEFORE THE FORMATION OF THE VENTRAL CANAL-CELL. 
The archegonia of Tsuga arise, as they do in other 
Gymnosperms, from superficial cells at the apex of the 
prothallium which cease to divide and become conspicuous 
for their large size and the abundance of protoplasm which 
they contain. Fig. t, Plate XXXI, shows one of these 
archegonial rudiments with its large nucleus and its radiating 
bands of protoplasm, which, in a later stage (Fig. 2) are 
confined chiefly to the upper portion of the cell, while the 
lower tapering portion is comparatively empty. Between 
these rudiments are other cells which continue to divide 
(Fig. 3) and later give rise to the archegonial sheath (Fig. 4). 
About one week after the differentiation of the archegonial 
rudiment, the neck-cell is cut off (Figs. 2-3). It at first has 
the form of a circular disk surmounting the central cell and 
equalling it in breadth but not in height. As the central cell 
grows, it appears comparatively narrow and more elongated 
and also shows considerable variation. In the greater 
number of well-developed archegonia, it divides into two cells 
about the time when the ventral canal-cell is formed 
(Figs. 4-6). The division-wall may be transverse, oblique, 
or longitudinal, but it is most often oblique. In many cases 
the neck-cell remains undivided, and, on the other hand, one 
