308 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
Polysiphonia violacea. Indeed, we have been forced to the opinion that the joint 
occurrence of sexual and asexual cells on the same plant is by no means an 
exceptional phenomenon, and Mr. A. D. Cotton informs us that he has noticed 
the same joint occurrence in Laurencia hybrida and Callithamnion sp. In his 
paper on Polysiphonia violacea (Bot. Gaz. vol. xlii. 1906, p. 401), Yamanouchi 
demonstrates, in that species, a regular alternation of generation between a 
gametophyte with 20 chromosomes and a sporophyte with 40 chromosomes. 
At the same time, he records under the head of ** Abnormalities,’ the occurrence 
of tetragonidia on eystocarpie or antheridial plants, and refers to simiiar cases 
noted by Lotsy in Chylocladia kaliformis, and by Davis in Spermothamnion 
Turneri and Callithamnion Baileyi. He adds,“ Such cases should be carefully 
investigated to determine whether true tetraspores are present or whether the 
structures are not really of the nature of monospores, as in Polysiphonia, and 
developed with a suppression of reduction phenomena." In the plants of 
Polysiphonia violacea collected by us in 1912 at Port Erin, Isle of Man, cysto- 
arpia and gonidangia were frequently present on the same branch, and the 
number of cases we met with, both in that species and in other genera, in our 
opinion, scarcely justifies the view that all of these are to be regarded as 
abnormalities. One of us is at present engaged on a detailed investigation 
of the matter from the cytological point of view, the results of which it is 
hoped to publish shortly. (See note, p. 309.) 
37. LOMENTARIA SQUARROSA, Käütz, 
38. HYPNÆA VALENTLE, J. Ag. (With eystocarpia and tetragonidia.) 
In this plant also we found both sexual and asexual reproductive organs 
in the same individual, indeed all the specimens were covered with “ fruit? 
of both types. The cystocarpia are of the normal //ypnea type. The tetra- 
gonidangia divide in a zonate manner and are formed abundantly from the 
superficial cells of ovoid pointed stichidia (fig. 3). The specimens were also 
interesting as exhibiting * Brutknospen,” or vegetative buds, closely resembling 
those of Sphacelaria. The adult form of these buds is stellate (fig. 4a, b, с, d), 
but all stages in their development could be readily traced on the same 
plant. 
*39. LAURENCIA OBTUSA, Lamour. (With eystocarpia and antheridia.) 
*40. DUDRESNAYA COCCINEA, Crovan. (With eystocarpia and antheridia.) 
*41. POLYSIPHONIA UTRICULARIS, Zan. 
42. LAURENCIA PAPILLOsA, Grev. (With cystocarpia.) 
*49. MELOBESIA THURETII, Born, (On Jania rubens, with cystocarpia.) 
*44. LITHOTHAMNION POLYMORPHUM, Aresch, 
*45. LITHOTHAMNIUM FASCICULATUM, Aresch. 
