Developmental Forms of Marine Alger. 
2 35 
Pig. 10.' It is true that the latter does sometimes assume a pro¬ 
cumbent form when attaching itself to other algae, and also puts 
forth little sucker-like rootlets from the hooked portions of the 
thallus, along the exterior margins and occasionally from the flat 
surfaces, Fig. 11 ; but here, 1 think, the connection ends. The 
structure of N.uncinatum is polystromatic, with oblong, cylindrical 
to hexagonal cells, Pig. 12. The sori are round and solitary, on 
short trifoliate obtuse lobes : they rarely occur on the frond itself. 
The whole genus Nitophyllum is very variable, and possibly of 
so plastic a nature that it responds readily to any stimulus; that of 
contact excites further growth, resulting in the development of 
suckers or rhizoid projections as need arises. 
In corroboration of these points Harvey has noted “ the 
marked difference between the same species found at different 
depths,” and again “ the tendency of specimens from deep water 
to form both hooks and discs, or supplementary roots, from various 
points of the stem and branches.” He also remarked that “ the 
outward habit is so completely changed by the production of 
hooked processes and discs, that it is difficult to discover the 
affinity of these distorted forms and such specimens have 
occasionally been unduly elevated to the rank of species.” 2 
Occasional dorsiventralism is not confined to this genus. It 
occurs in Gelidium crinale, a plant usually erect in habit, but it 
has been found at low tide creeping over Lithothamnion poly • 
morphum, when it sends down little root-like suckers from its 
undersurface. Intermediate stages exist in sandy conditions where 
the plant is partially erect, partially creeping. The interlacing 
fibres serve to hold the sand together and form tufts or knots of 
vegetation, Fig. 13. Yendo 3 refers to Gloiopeltis and other 
algae, which are membranaceous in the embryonal stage adhering 
firmly to the substratum. Doubtless other instances will he forth¬ 
coming as a result of further research. 
Recrudescence. PI. I, Figs. 1-2 and PI. II, Figs. 1-3. 
Certain lateral and superficial growths have been noticed on 
the older plants of several species, and questions as to their 
biological significance naturally arise. 
1 Cotton, U)ll. Clare Island Survey, p. 136. 
1 W. H. Harvey, Substance of a course of Lectures on Marine Algae, 
1856. Opuscula Crypt. LXXIII, p. 87. 
3 Yendo. Economic Proc. Roy. Dublin Soc., V, II, No. 7. March, 
1914, p. 118. See footnote. 
