400 
Mot tier. — Contributions to the 
antheridial cavity is roofed over by a layer of two, occasionally 
three, cells in thickness. As the antheridia approach maturity 
they gradually burst through this roof, the cells of which 
separate near the centre and turn back, forming the edge of 
the cup-shaped cavity in which antheridia of different ages 
stand side by side. The cells of the roof, at the time of 
opening, appear more rounded, with thinner walls, so that it 
seems that a dissolving agent acts with the mechanical 
pressure of the antheridia. Very frequently there are much 
younger antheridia in the same cavity with the mature ones, 
a fact which seems to give further evidence of an endogenous 
origin. 
The development of the antheridium of Notothylas is pre- 
cisely like that of Anthoceros . 
Summary. 
The results of c the foregoing statements may be summed up 
as follows : 
1. The capsules of Notothylas orbicularis , Sulliv. possess 
a columella varying in size with that of the capsule. 
2. The columella originates, as in Anthoceros , primarily in 
the young sporogonium with the archesporium, and inde- 
pendently of it, and consequently it is not a secondary differ- 
entiation within the spore-chamber. 
3. The archegonium of Notothylas resembles more closely 
that of the eusporangiate Ferns than does the archegonium 
of Anthoceros. 
4. The antheridium arises from a hypodermal cell, a pro- 
cess occurring nowhere else in the whole group of Bryophytes. 
I desire to acknowledge my indebtedness to Dr. L. M. 
Underwood for the use of important and necessary literature. 
