1 82 Atkinson . — A Monograph of the 
the sexual shoot. These are the most conspicuous parts of 
the plant and those usually taken by collectors. They 
originate as special lateral shoots from the Chantransia-i orm. 
They begin their development late in autumn or early winter 
and reach maturity late in the following spring or early 
summer. 
The most characteristic stage of the sexual shoot is during 
the period of fertilization, which occurs at a variable time 
from January to March. The time depends largely upon the 
temperature of the stream as determined by climatic con- 
ditions or altitude. They occur usually in dense circumscribed 
tufts or in extensive mats, covering sometimes several square 
feet of rock-surface. The individual sexual shoot is simple or 
very much branched, and rather stoutly filiform. At regular 
intervals there are plane or papillate enlargements, sometimes 
very prominent. At this stage they are of an olive-yellow, 
greenish, or violet color, and commonly from 2 cm. to 16 cm. 
long, and being flexible, lie in the direction of the current, or 
are arcuate. At the period of fertilization the enlargements 
can well be seen with the unaided eye ; sometimes they are 
much more prominent at maturity and sometimes less so. 
Figs. 56 and 57 represent two sexual shoots, natural size. 
If this simple description has enabled the reader to recog- 
nize the plant at this period of its development, the external 
characters which separate the family into two natural groups 
may be pointed out. To one familiar with these characters 
such a determination could usually be made at sight without 
the use of any magnifying power. A small hand-glass, how- 
ever, will enable any one to recognize these characters at the 
time of fertilization. 
I will select as a representative of the simpler group a 
widely distributed and very variable species, Lemanea fiLcina 
Bory, so named because of its resemblance to certain species 
of a filiform Fucus 1 . By examination with the hand-lens the 
enlargements will probably resemble one of those illustrated 
1 Bory, Ann. d. Mus., etc., loc. cit. 
