234 CR YPTONEMIA CEJE. PART n. 



eighteen, or even twenty, and form the characteristic of 

 the genus. Thus there is a similarity of structure be- 

 tween the Pplysiphonia, a genus of the highest order 

 amongst Rhodosperms, and the Griffithsia, which is one 

 of the lowest. The Polysiphonia elongata, which is 

 from six to twelve inches high, has four primary and 

 several secondary colour tubes in the transparent joints 

 of its filaments. Like many of its congeners, this plant 

 does not come to perfection or bear fruit till the second 

 spring. In its youth, it resembles the full grown plant 

 but is smaller, and the colour tubes are not formed in the 

 capillary threads of the tufts, which with many of its 

 branchlets are deciduous, leaving the plant in its naked 

 winter state. With returning warmth, it assumes 

 its perfect form, and in March and April- bears fruit, 

 which consists of nuclei in conceptacles, sessile on the 

 branches, either clustered or scattered. The spores are 

 at the top of jointed threads rising from a substance at 

 the base of the nuclei. In some species of this genus, 

 tetraspores only have been found. 



The Cryptonemiacese are the most numerous and di- 

 versified of all the orders of the Rhodosperms. Thirty- 

 five genera are widely dispersed throughout the world, 

 chiefly in the northern hemisphere ; twenty-four genera 

 at least occur on the east coast of North America; 

 and fifteen genera have representatives in the British 

 seas. This multitude of generic forms is divided into 

 two groups of gelatinous structure, the one having in- 

 articulate fronds composed of articulate threads closely 

 incorporated, the other membranaceous, formed of 

 cells closely incorporated into a foliaceous expansion. 

 Most of these plants have a stratum of cellular tissue, 

 interposed between a spongy matter in the interior 

 of the frond, and the epiderm or external skin, which 

 for the most part consists of a simple layer of minute 

 cells firmly united by their sides, generally forming 



