in Rhodymeniales : IL Delesseriaceae. 175 
only upon the generic position of D. sanguined , but even 
upon its ordinal place. I propose to recur to this question 
later. 
The segments of the thallus of D. sanguinea simulate the 
appearance of leaves to a remarkable degree. As, however, 
Goodenough and Woodward (1795) long ago remarked, ‘when 
attentively considered and compared with others, they appear 
to be branches growing up into, or dilated into, a thin mem- 
brane.’ The rudimentary plant consists of a leaf-like lamina, 
attached by a holdfast. In course of time the winged portion 
of the thallus disappears, and further growth is provided for 
by proliferation from the persistent, more or less cylindrical 
midrib. I believe that in this species a new series of pro- 
liferations occurs every year, and that therefore the age of 
the plant can be accurately measured by counting the joints 
of the sympodium, of which the plant, from the holdfast to 
the still growing apex, consists. Among the first prolifera- 
tions of each recurring period of growth the fertile shoots 
arise in great numbers (Fig. 1 ). Occasionally the winged 
portion of an old shoot may persist for some time after the 
proliferations of a new period have begun to grow, in which 
case the fertile shoots appear in two rows, right and left of the 
midrib, on each surface of the leaf-like shoot. These fertile 
shoots are at first precisely similar in appearance to the 
corresponding stages of the sterile shoots, but remain small 
in comparison to the later stages of the latter. The pro- 
duction of reproductive organs, whether tetrasporangia or 
antheridia or cystocarps, seems to drain the resources of the 
shoots and to dwarf their vegetative growth. Whilst the 
sterile shoots of one period may reach many inches or even 
a foot in length, the tetrasporiferous shoots are hardly more 
than half an inch long, and the antheridiferous and cysto- 
carpic shoots are even less. I believe, however, that when 
fertilization fails, procarp-bearing shoots may, and often do, 
take on again the vigorous apical growth of the sterile shoots, 
and later become indistinguishable from them. 
When, however, fertilization does take place, the female 
