Fertilization in Sphaerocarpos. 
BY 
H. W. RICKETT. 
With Plates III and IV and three Figures in the Text. 
Introduction. 
T he details of the process of fertilization have been very thoroughly 
studied in examples of all the great groups of plants save the 
Bryophyta. In this group no complete cytological account of fertilization 
has been published for any form. A few scattered observations, ranging 
from the beginnings of cytology until recent times, make up the literature 
on the subject. This condition is partly due, no doubt, to technical obstacles 
in the study of the mature archegonium, owing to the formation of a laige 
quantity of mucilaginous material through which the antheiozoid passes to 
the egg and which renders fixation difficult. 
The earliest account of fertilization in a Liverwort was given by 
Strasburger ( 1870 ) for Marchantia polymorpha. He described the egg as 
having an apical colourless receptive spot. He figured the swarming of 
antherozoids around the end of tne neck of the open aichegonium, in the 
extruded mucilage, and was able to distinguish single antherozoids in the 
neck. They were too small for him to follow farthei. As to dieii fate 
when they reach the venter, he says : 
‘ Doubtless they are taken in by the receptive spot. Whether here, as 
in ferns, one spermatozoid is enough to complete fertilization could not 
be made out; from the size of the egg and the receptive spot in comparison 
with that of the spermatozoid, I might conclude that there are heie a largei 
number of the latter taken into the egg.’ 
The first to concern himself with the cellular details of the sex organs 
of a Liverwort was Kruch ( 1891 ), who gave a careful and fairly complete 
account of the development of the sex organs and of fertilization in Riella 
Clausonia. His paper is of especial interest in that his account of fertiliza¬ 
tion can be very easily harmonized with that which is here presented for 
Sphaerocarpos , a form thought by many to be closely related to Riella. 
[Annals of Botany, Vol. XXXVII. No. CXLVI. April, 1923.] 
