FIL'ICINE.E. 
segments in two rows are at first formed from it by walls inclined upwards and 
downwards ; the dorsal median leaf also proceeds from the first dorsal segment. 
But a different arrangement is soon produced as the plant increases in strength; 
the apical cell of the stem forms segments arranged in three rows with a ^ diver- 
gence, and in such a manner that one row of segments comes to lie below (ven- 
trally), while the two other rows form the dorsal side of the stem. The ventral side 
of the stem forms roots in strictly aero petal succession, as in Azo//a, the youngest 
being found near the apex of the stem. On the dorsal side of the stem the 
leaves arise in two alternating rows, some of the dorsal segments remaining at 
the same time sterile and serving for the formation of internodes. The first leaf 
of the young plant, lying in the median line and without a lamina, is followed, 
in the biseriate arrangement which now results, by a number of young leaves with 
a short stalk and a lamina at first entire but afterwards divided into two and 
four lobes; normal leaves, circinate in their vernation, are then for the first time 
formed with a long stalk and a quaternate lamina. In the processes which have 
now been described, Pilularia agrees, according to Hanstein's observations, with 
G g 2 
