and Polyides rotundus. 95 



0-0820"'; O-OeSS'"; 0-0739'"; 0-0848'"; 0-0752'"; 0-1006'"; 

 0-0900'"; 0-1062'"; 0-0933"'; 0-1072'"; 0-1144'"; 01153'"; 

 0-1197'"; 0-1120'"; 0-0811'", giving an average of 0-0934'" par. 

 These cells show no sort of '^anastomosis/' and there is no 

 sort of cells in the stem of Polyides rotundus which is " dicho- 

 tomous." 



The stems of Polyides rotundus are all fixed, with one common 

 large disc from which new stems originate. The construction of 

 the disc of the points of the growing stems and their attenuated 

 base is like that of the corresponding parts in Furcellaria fasti- 

 giata, with scarcely perceptible differences. 



Polyides rotundus has two sorts of fruit. The epidermal outer 

 layer of the stem produces outwardly, as a continuation of its 

 own radiating epidermal cells, strings of small cells, the relative 

 proportion of which in breadth : length is = 1 : 1-6. The strings 

 of these cells run parallel to each other, cohering laterally by 

 being imbedded in a transparent, colourless, slimy mass ; the 

 contents are a whitish granular substance. 



These strings of cells form laterally on the upper part of the 

 branches rounded protuberances, surrounding i or f of the pe- 

 riphery of the stem, being 1-1^ line thick and 1-4 lines long. 

 Between these strings of cells are found singly-lying very large 

 elliptical cells, with colourless transparent walls, containing crim- 

 son-coloured pear-shaped spores in great quantity, placed with 

 their acute point to the centre of the cell. These clusters of 

 crimson- coloured spores give the whole protuberance to the 

 naked eye a rose-red colour. Fig. 20 exhibits such a cluster of 

 spores with the surrounding strings of cells ; c-d is the epidermal 

 stratum of cells in the stem. 



There does not exist any epidermis in these protuberances, as 

 Greville rightly observes, although Harvey (fig. 1 & 5. pi. 95 in 

 his Phycol. Brit.) conveys the idea of there being epidermis. 



The other fructification of Polyides rotundus, which up to this 

 time seems only to have been found by Mrs. Griffiths near Sid- 

 mouth, but was found also by me in specimens which were col- 

 lected in January 1850 at Cromer, are tetraspores mostly divided 

 crosswise, under the outer epidermal stratum in the swollen up- 

 per parts of the ramules. These tetraspores are elliptical, often 

 not parted in four, but only in two or three sporules. Fig. 21 

 exhibits a part of a transverse section of a swollen ramule, with 

 three tetraspores and one which is abortive. Fig. 22 & 23 show 

 two spores parted crosswise ; fig. 24 & 25 two, which only con- 

 tain three spores, and fig. 26 & 27 two, only containing two : 

 it might be thought that the two last are nothing else but four 

 parted spores seen from the side ; but this is not the case with 

 those I figure, as I had opportunity of convincing myself. 



