296 PERCY SLADEN TRUST EXPEDITION 
The central cell is surrounded normally by four pericentral cells, but between these 
other large cells soon appear and numerous hyphe develop in the membranes. I have 
not seen them enter the pericentral cells as they do in 7. Bornetit, but it may be that 
this takes place in the basal part of the frond. A layer of small cortical cells surrounds 
the main axis. The latter has a winged appearance on account of the pericentral cells 
of the spine-like lateral branches growing sideways together with it for a few segments. 
Adventitious branches appear occasionally on the dorsal side of the frond in the axil 
of lateral branches, but they remain short; in 7. Bornetii these branches attain full 
development. 
The characteristic dorsi-ventral organization of 7. Bornetii is far less conspicuous in 
T. Ethele, and shows itself in barren specimens only in the rudimentary axillary 
branches. No organs of fructification were present, and it was only because I was 
familiar with the genus that I was able to name the specimens from Amirante. 
HETEROSIPHONIA, Montagne. 
1. HerrrostpHontIa RENDLEI, n. sp. (Plate 16. figs. 11, 12.) 
Thallo fasciculato, pluribus ramis principalibus e callo basali surgentibus; ramis 
principalibus totis ecorticatis, pauce ramosis, penicillos ad segmentum quodque 
secundum, distichos et alternantes gerentibus. Cellulis pericentralibus 7—S-10. 
Penicillis ramulos unilaterales et stichidia potius obtusa quam acuta ferentibus 
tetrasporis instructis. Antheridiis et cystocarpiis ignotis. Thallo alto 8 cm. 
Cargados Carajos, 47 fms.; dry specimen. 
I believe Heterosiphonia Kendlei* to be a new species because none exists amongst 
the Heterosiphonie ecorticate that is exactly like it. It belongs tothe small group with 
more than four pericentral cells, the branches or penicilli of which arise at a distance 
of two or three segments from each other and are turned regularly to the right and 
left. H. Rendlei stands nearest to H. subsecundata (Suhr), Falk., but differs in the 
pericentral cells not being transversely divided. 
The principal axis has a height of about 8 em.; it is erect and carries small horizontally 
spread penicilli which have unilateral monosiphonous branchlets incurved at the top. 
The number of pericentral cells in the main axis varies from 6-10, and the segments 
are three times as broad as long. In the penicilli the few basal polysiphonous segments 
are almost as long as broad or a little broader. 
I have seen neither cystocarps nor antheridia, only stichidia, which are borne on the 
side-branches of the penicilli; they are elongated with a blunt apex. 
2. HETEROSIPHONIA spec. 
Coetivy, reef; dry specimen. 
This is a small specimen, 1 cm. high; it grows on Codiwm. I failed to recognize it 
amongst the described species and yet do not dare to describe it as new. 
* Named in honour of Dr. Rendle, Keeper of the Botanical Department of the British Museum, renowned for 
the kind hospitality that it offers to every visitor. 
