136 A. H. Graves, 
Before I leave the account of the megasporangium, two cases in 
which the archesporium was undoubtedly two-celled should be 
recorded. Murbeck (1902, p. 14 and figure 35) has figured a double 
megaspore mother-cell, which, however, according to his explanation, 
is caused by the very oblique orientation of the wall between 
primary parietal and primary sporogenous cells, making this wall 
almost perpendicular to the epidermis and hence resulting in two 
large cells, apparently both potential megaspore mother-cells, and 
bounded exteriorly by the epidermis. 
But my first illustration (Pl. XI, fig. 77) shows a clearly differ- 
entiated, single, parietal layer and two large megaspore mother- 
cells with their common wall very distinct and quite perpendicular 
to the epidermis. The second example has developed somewhat 
further (Pl. XI, fig. 78), the two megaspore mother-cells having 
passed through the first division, a cross wall being formed, which 
divides each into two essentially equal daughter-cells. Here may 
also be noted the rather uncommon occurrence of two parietal layers. 
On the analogy of the microsporangium of Angiosperms, it would 
seem most natural that multicellular archesporia should occur also 
in the megasporangium. Through the investigations of Strasburger 
(1879), Fischer (1880), and among others, especially Péchoutre (1902), 
we have come te know that such a multicellular archesporium is 
quite general in the megasporangia of the Rosaceae; and that it 
also occurs in many other dicotyledonous groups has been sufficiently 
proven. 
On the other hand, the reports of an archesporium of more than 
one cell in the megasporangium of monocotyledons are meagre, 
and, as reviewed by Coulter and Chamberlain, may be embraced 
in two cases, Ornithogalum pyrenaicum (Guignard, 1882), and 
Lilium candidum (Bernard, 1900). In these instances the archesporium 
is presumably always more than one-celled. There are, however, 
many Cases, such as some of the Ranunculaceae, when the archespo- 
rial cells vary from one to many (Mottier, 1895, and Coulter, 1898). 
To such as these last the condition in Ruppia maritima is similar. 
FEMALE GAMETOPHYTE 
As it is now regarded, the history of the female gametophyte 
commences with the preparations for the first division in the mega- 
spore mother-cell. As regards this preparatory stage, I find that 
Ruppia maritima does not deviate essentially from R. rostellata, 
ee es 
