Notes. 
151 
PRELIMINARY NOTE ON THE REPRODUCTION OF RHODYMENIA 
PALMATA, A g.—In spite of the large amount of material of Rhodymenia palmata , 
Ag., available on the shores of the Northern Hemisphere, no account of sexual repro¬ 
duction in this species has been published. Indeed, as recently as 1919,01*. Church 1 
cited this alga as an example of a member of the Rhodophyceae in which the sexual 
phase might be regarded as omitted from the life-cycle. 
Asexual reproduction . Asexual reproduction is known to take place by means 
of tetraspores embedded in the outer small-celled tissue of the thallus, ‘ scattered or in 
cloudy patches ’. 2 
These tetrasporic thalli were found in large numbers, both in the spring and 
!ig. 1. Transverse section of a tetrasporic thallus of Rhodymenia palmata, showing the 
scattered groups of tetraspores embedded in the tissue forming the outer cortex of the thallus. Camera 
lucida outline, x 250. 
autumn (April to September), at Shanklin, Isle of Wight. The tetrasporangia were 
either— 
1. Scattered singly in the cortical tissue of the thallus (Fig. 1), giving the frond 
a mottled appearance in surface view ; or, 
2. Aggregated in sori, which may be marginal or may occupy the centre of the 
frond. 
Sexual reproduction. The procarpial fronds were first found in April 1922, in 
some material gathered at random from the rocks at Shanklin. 
These fronds are similar in form and colour to the vegetative or tetrasporic ones, 
but on examination the upper part of the frond is seen to be thinner and paler in 
texture than the rest, and is covered with minute, dark, ill-defined spots which sections 
show to be groups of procarps. These are developed on both surfaces of the fronds 
and are not scattered, but are aggregated into small groups situated near each other 
and arranged in regular acropetal succession. 
The procarps are developed from among the smaller cells of the outer thallus 
tissue; when first differentiated each procarp consists of one or two cells (Fig. 2, a), 
but later these divide, giving a chain of three or four (Fig. 2, b). The upper cell 
1 Church, A. H.: Historical Review of the Florideae. Journ. Bot., lvii, 1919, p. 329. 
2 Harvey, W. H. : Phycologia Britannica, 1871, vol. iii. 
