and Fertilization in the Hemlock Spruce . 599 
zone the egg shows its normal structure. The cause of this 
hyaline zone is difficult to determine. It appears that the 
stored food has been taken from this region in order to 
provide for the growing want of supplies for the nuclei below ; 
but since the remaining available contents of the egg are 
doubtless also transferred to the developing embryo, there is 
no apparent reason why this zone should be left. It possibly 
represents an intermediate condition of these contents in which 
they do not easily take or retain stains. 
Summary. 
The archegonia of Tsuga originate as single superficial 
cells, in each of which occurs the usual division cutting off 
an outer smaller cell that forms the neck. At maturity, the 
neck most commonly consists of two cells, though in very 
many cases the neck-cell fails to divide at all. Three and 
four cells in the neck are less commonly observed. 
In the division of the central cell the spindle-fibres arise 
from a large dense fibrous mass beneath the nucleus and grow 
into the nuclear cavity, where they are later joined by fibres 
from the very small upper pole. The division resembles that 
recently described for many vegetative cells, but belongs to 
a new and distinct type hitherto undescribed. The mass of 
cytoplasm at the lower pole with its extensive radiations 
suggests a huge centrosphere. 
As the egg-nucleus increases in size and moves to the centre 
of the egg, the vacuole moves upward, passing it on its way, 
and comes to lie near the egg-apex. Just beneath the ventral 
canal-cell may always be found another somewhat smaller 
vacuole with contents similar to those of the nucleus. These 
vacuoles form the receptive spot of the egg. 
The contents of the pollen-tube cast into the egg consist 
of the vegetative nucleus with some cytoplasm and starch- 
grains, the stalk-nucleus surrounded by its own scanty, vacuo¬ 
late cytoplasm, and the two unequal sperm-cells with their 
dense cytoplasm and large deeply-stained nuclei. The larger 
