9 6 
Ford . — The Anatomy of 
troides and Parkeria pteroides. The name Parkeria was 
given by Hooker and Greville 1 to a Fern in 1824, at a time 
when very little was known of the genus Ceratopteris. The 
plant examined by Hooker and Greville was characterized by 
the reduction or complete absence of the annulus on the 
sporangium, and this feature, together with the fact that the 
Fern which had been named Ceratopteris three years before 
was practically unknown to them, induced the investigators 
to create a new genus Parkeria. In Hooker’s ‘ Species 
Filicum,’ however, published in 1858 2 , the genus Parkeria is 
omitted, and the author states in a note at some length, that 
since the publication of the ‘ Genera Filicum ’ he has modified 
his former views, a detailed comparison of the two Ferns 
having shown him conclusively that they must be regarded 
as belonging to the same genus, and must for the future be 
included under the single genus Ceratopteris. 
Ceratopteris thalictroides is an annual aquatic Fern, which is 
found growing in the Tropics in marshes, pools, and running 
streams. In shallow water the plant roots in the mud at the 
bottom ; in deeper water, however, it is found floating freely. 
In some rivers it is reported as being exceedingly abundant, 
almost blocking up the stream with its growth. The plant 
has a wide geographical distribution, being found practically 
in all tropical regions of the globe. It has been reported 
from Mexico and southwards as far as Brazil, from the West 
Indies, the West Coast of tropical Africa and Madagascar, 
and from the Punjaub southwards to tropical Australia. In 
the Indian Archipelago the plant is cooked and eaten by the 
natives as a vegetable. 
I. External Morphology. 
Owing to the great reduction of the stem, the most notice- 
able part of the mature plant lies in the leaves. These are of 
two kinds, the sterile and the fertile, the latter bearing on 
their under-side numerous scattered sporangia. Hooker, in 
1 Hooker and Greville, 1824. 
2 Hooker, 1858, p. 236. 
