Form of Hormidium Jlaccidum , A. Braun. 525 
more or less spherical in form, though tending to assume an irregular shape 
when large. They vary considerably in size, being often scarcely visible 
under a magnification of 3,000 and passing through all gradations to 
a diameter of about 4 /x (Fig. 4, L). When present only in small numbers, 
they lie here and there in the surface layer of the protoplasm, most 
commonly near the septa. If exceedingly abundant, they are concentrated 
at the ends of the cells, but may also be numerous in the part of the proto- 
plasm between the two longitudinal edges of the chloroplast (Fig. 4, M) ; 
occasional granules are always scattered in the surface protoplasm adjacent 
to the chloroplast During the earlier stages of accumulation, the cells are 
usually vacuolar, as described above (p. 512), and the first-formed granules 
appear mostly at the surface of the vacuoles (Fig. 4, n). In the later stages, 
the masses of granules at the ends of the cells frequently preserve the out- 
lines of the vacuoles and can be seen to have entirely occupied the latter. 
This suggests that they are produced as a result of changes occurring 
chiefly in the contents of the vacuoles (cf. p. 533). 
Granules similar in appearance have been found in other forms 1 of 
Hormidium flaccidum distinct from the Woodford Alga, and in Spirogyra , 2 
Prasiola , and Pleurococcus. 
Gay 3 has recorded the accumulation of oil globules in Hormidium 
dissectum ( Ulothrix dissectd) when growing in water, and Klebs 4 has stated 
with reference to H. nitens that the cells become filled with drops of fatty 
oil when subjected to slow desiccation. Klercker, 5 in Siichococcus subtilis , 
described droplets, which he called ‘ spherules ’, usually present in the polar 
vacuoles, 6 but sometimes * accumulating in such abundance as to make an 
examination of the internal structure of the cell almost impossible \ Apart 
from their similar disposition in the cells, these bear a striking resemblance, 
as shown in the figures, to the granules of Hormidium. Klercker 7 states 
that they agree in many respects with the substances occurring in Stigeo- 
clonium and other Chaetophoraceae. The globules of Zygnema ericetorum 
described by Fritsch, 8 West and Starkey, 9 and de Bary 10 are somewhat 
similar in form and appearance to those of Hormidium flaccidum and 
1 Viz. (i) a narrower form, with filaments of average width 5*7 p., growing at Loughton, Epping 
Forest; (ii) a wider form growing on Hindhead Common. I have to thank Dr. Fritsch for the 
information regarding this Alga, and for material. 
2 Probably tannin-vesicles. Cf. Czapelc : Biochemie der Pflanzen, vol. ii, 1905^.579; Hill 
and Haas : The Chemistry of Plant Products, 1912, p. 191. They take on a brown coloration with 
osmic acid similar to that produced by the latter in the granules of Hormidium. 
3 1. c., p. 62. 4 1. c., p. 340. 
5 Klercker : Ueber zwei Wasserformen von Stichococcus. Flora, vol. lxxxii, 1896, pp. 92, 93. 
6 These resemble, in form and disposition, the vacuoles of the Alga dealt with in this paper. 
7 1. c., p. 92. 8 F. E. Fritsch, 1. c., p. 143. 
9 G. S. West and C. B. Starkey : A Contribution to the Cytology and Life-history of Zygnema 
ericetorum (Kuetz.), Hansg. New Phytol., vol. xiv, 1915, p. 197. 
10 de Bary : Unters. liber die Familie der Conjugaten, Leipzig, 1858, p. io, PI. I, Figs. 16, 20. 
N n 2 
