RHODOSPERME. 115 
ramuli the siphons are two or three, and are twice or thrice as long as broad. 
P. elongella, in its summer state, is a highly beautiful plant. It bearsa 
strong resemblance to P. elongata (Fig. 104), and, like that species, being 
biennial, is unsightly during winter, but in spring is clothed with tufts of 
fine rose-red ramuli. The joints of the stem and main branches are all 
distinctly marked, and are of equal length and breadth. The siphons are 
six or seven, and are separated by beautifully pellucid spaces. This species 
is rare, but widely distributed. I have taken it in Scotland and on the 
south Devonshire coast. P. atro-rubescens is a species which I have taken 
in Torbay and in Whitsand-bay only. It may be known by the little 
bundles or bunches of pointed ramuli which are produced alternately along 
Fie. 107. Polysiphonia byssoides ; (a) Branch with capsules; (b) Branch with 
tetraspores. 
the stems, somewhat in the same manner that similarly-tufted branchlets 
are set on the branches of Rytiphlwa fruticulosa (Fig. 99). Under the 
microscope the tubes in the articulations appear to be spirally curved, a 
character which serves to mark this species. A transverse cutting of the 
stem reveals twelve or thirteen siphons. P. Agardhiana is a small 
variety of this species. P. pulvinata, now P. sertularioides, is a small 
summer annual, growing on rocks and alge in dense intricate tufts rarely 
more than lin. high. P. spinulosa is an extremely rare species found at 
Appin by the late Captain Carmichael. I possess a single specimen of 
this plant, taken at Plymouth many years ago, and ever since I have 
looked for it in vain. P. Richardsoni, taken on the coast of Dumfries 
