386 PERCY SLADEN TRUST EXPEDITION. 
which conceals the main filaments in Udotea argentea, Zan., and other species, but they 
can be detected by a lens as standing out along the main filaments even before the plant, 
whether dry or moist, has been decalcified. In Decaisne’s type the branchlets are more 
short and simple than in Chauvin’s specimen, where each lateral branchlet frequently 
divides into two or three points. The plants from Cargados Carajos resemble the type 
in this character, and have mostly simple, short, pointed branchlets. | 
26. Udotea argentea, Zanard. Plant. Mar. Rub. in Mem. R. Ist. Ven. vol. vii. (1858 
p- 290, tab. 10. figs. la, 1. . 
f. typica, form. nov.; ramulis lateralibus capitatis; capitibus varie angulatis aut 
lobatis. 
Coetivy, on reefs exposed at dead low tide. Cargados Carajos, 22, 30, and 47 fms. 
Geogr. Distr. Red Sea. 
This species is not a well-known one, but it is so well marked that, when once 
recognised, it is quite unmistakable. The figures given by Zanardini (/. ¢.) of the 
original plant, collected by Portier at Suez, are quite sufficiently good to identify this 
characteristic species, even despite the loss of Zanardini’s type, which has been searched 
for in foreign herbaria in vain. In habit U. argentea is often repeatedly proliferous, 
the proliferations overlapping each other so thickly at times that a single plant forms a 
sort of fan-shaped’ colony. The structure is, generally speaking, like that of other 
corticated species of Udotea, but it is distinguished from all of them by the character 
of the lateral branchlets. In U. argentea these arise at short intervals in two or three 
rows along the main filaments and bear each a head which is variously angulate or 
lobed. These capitate lateral branchlets soldered together by a deposited cement of 
calcium carbonate form a strong cortex, and thus unite into a firm frond the parallel 
main filaments, which form the framework of the thallus. The variations in the form 
of the head of the lateral branchlets are sufficiently marked to allow of the species being 
divided up into several forms, which appear to have also a more or less definite 
geographical distribution. The form represented in the present collection is the one 
which we regard as a typical representative of the original plant from the Red Sea, and 
we call it therefore f. ¢ypica. Other forms will be described and figured by us in our 
account of the Udotee collected by Madame Weber van Bosse during the ‘ Siboga’ 
Expedition. 
Since the above remarks were written, we have recently had the great satisfaction of 
examining what we had long desired to see, namely, specimens of U. argentea from 
the Red Sea, and actually from the type-locality. These were included among some 
unnamed specimens submitted to us by Prof. R. J. Harvey Gibson and had been 
collected by Mr. C. Crossland at Suez Bay. They have since been embodied in 
Prof. Gibson’s paper read before the Linnean Society on December 5th, 1907. 
Mr. Crossland’s specimens supply just the geographical link which we desired for 
the completion of the chain of proof that we had rightly referred the Indian Ocean 
specimens to the U. argentea, which had previously been recorded only from the 
ted Sea. The Suez Bay specimens exactly resemble those of Mr. J. Stanley Gardiner, 
while further to the east, as shown by specimens from the Malay Archipelago (‘ Siboga’ 
[ 76.4 
