46 Lang. — Prothalli of Ophioglossum pendulum 
dehiscence-cells, of which several are present, do not undergo 
the periclinal division ; only one of these cells breaks down on 
the opening of the antheridium. 
5. The structure of the archegonia, which have long necks, 
like those of Botrychium , was not satisfactorily determined. 
6 . The old embryo resembles that of Botrychium ; it has 
a large foot ; the primary root, first leaf, and the stem-apex 
seem referable to the epibasal half. 
7. The young plant remains attached to the prothallus until 
several leaves are formed. The first leaf has a ternate lamina 
and reaches the light. For a time a single root is developed 
below each leaf. 
8. The first root is triarch, succeeding ones tetrarch. A 
mycorhizal Fungus is present in a medio-cortical zone of the 
first few roots. 
9. The stele of the stem is at first endarch and maybe solid 
or have a small pith ; it is surrounded by a well-marked 
endodermis. The first leaf-traces are endarch or mesarch and 
do not leave definite leaf-gaps. 
10. Gwynne- Vaughan’s organ is present even in relation to 
the first leaf. 
Comparative Remarks. 
Although for the sake of completeness the anatomy of the 
young plant of Helminthostachys has been included in the 
preceding description, the following discussion will have 
reference only to the evidence as to the affinity of the Ophio- 
glossaceae afforded by the gametophyte. The relative 
independence of the two generations in the Pteridophyta 
appears to justify such a separate consideration. The em- 
bryogeny may, however, be conveniently considered along 
with the prothallus, since the structure and mode of life of 
the latter are important factors in the environment of the 
embryo. 
The prothalli of the three living genera of Ophioglossaceae, 
while differing in details, present essential points of agreement 
with one another. They are all wholly saprophytic and live 
