218 Dr. Greville on some new species of Sargassum. 



vesiculis elliptico-sphsericis petiolatis, petiolis foliaceis, dilatatis ; 



receptaculis compressis, valde dentatis, in racemo composito ag- 



gregatis. 

 Wight in herb. no. 17. 

 Hab. in mari Peninsulae Indise Orientalis ; Wight. 



Root a callous disc, throwing up a number of stems nearly two 

 feet long, compressed, a line or more broad, undivided, giving off 

 branches in a distichous manner, at intervals of from half an inch 

 to an inch or more, 3-6 inches long, spreading, the whole forming 

 a more or less oblong outline. Fruit-bearing ramuli numerous, 

 an inch long or more at the base of the branches, and dimi- 

 nishing gradually to the extremity. Leaves : those produced 

 from the main stem and especially on young plants often 2 to 

 near 3 inches long, and from a quarter to half an inch in breadth, 

 somewhat obtuse at the apex, either quite entire or obscurely 

 repando-dentate, rarely furnished with a few sharp teeth towards 

 the base. On the branches they are about an inch long, more 

 or less lanceolate, more acute, often sharply toothed ; all furnished 

 with a nerve and pores. Vesicles somewhat elliptical, on young 

 plants nearly as large as a small garden pea, supported on foli- 

 aceous, dilated stalks 2-3 lines long. Sometimes the vesicle is 

 winged and apiculate. Receptacles 1-1^ line long, axillary, 

 forming pedunculate, more or less divided racemes, the segments 

 very irregular in shape, compressed, and toothed so as frequently 

 to resemble a deer's horn. 



The most remarkable feature in this Alga is the occasional 

 length of the leaves which ai'ise at the base of the primary 

 branches, and which cause them to resemble the fronds of some 

 of the Lycopodoid Polypodia. This is most conspicuous in a 

 rather early stage of growth. The species however is liable, I 

 suspect, to considerable variation ; and even on the same indivi- 

 dual leaves may be seen almost, if not quite entire, while others 

 are decidedly and sharply toothed. The latter occur chiefly in 

 the upper part of the plant, and towards the ends of the branches. 

 The description and figure I have given must be regarded as pro- 

 visional, for if my apprehensions be well-founded, a more exten- 

 sive series of specimens will be required before a complete cha- 

 racter can be drawn up. 



EXPLANATION OF PLATE IX. 



Sargassum obovatum. 



Fig. 1. Termination of a branch. 



— 2. Canhne leaf". 



— 3. Leaves accompanying the receptacles. 



— 4. A raceme and leaf from the end of a branch. 



— 5. Vesicles. 4 magnified. 



