98 MEMOIR V. 



while its flexuose shoots often extend to the length of 

 several inches, very much like the plant from which it has 

 ohtained its trivial name (viz. Cuscuta or Dodder.) The 

 main stems originate from tubular creeping roots, which 

 invest marine plants in shoal water, these stems are often 

 jointed at unequal distances, and give off a number of short 

 branches, which originate in pairs from its opposite sides, 

 frequently just above a visible joint; these branches 

 support the vesicles, which are scattered over their surface 

 in an irregular manner, and do not differ except in size 

 and number of tentacula, from those of V. imbricata ; the 

 tentacula being 8 in number, (f. 4.) 



Vesicularia spinosa (Sertularia of authors) (PI. III. f.l.) 

 is indeed a production of the greatest beauty and delicacy 

 when in its prime, and of quite a peculiar air and habit, the 

 vesicles however with their animals exactly accord with 

 those of the last species, only that the former are more 

 turgid or of an oblong oval shape. The stem in this species 

 rises from a tuft of tubular intricate roots, and is more or 

 less thick in proportion to the age of the individual, a 

 circumstance also met with in some of the true Sertularia 

 (viz. Campanularia verticillata and Sertularia Halecina,) 

 and as its thickening arises from the constant addition 

 of fresh radical tubes to its outer surface, it is probable that 

 every new branch in these species sends downwards its 

 radical tube along the surface of the stems, so as to give 

 them the requisite strength, in proportion to the growth of 

 the upper part ; this stem sends off branches in an alternate 

 and irregular order, which are erect and zigzag, and 

 become extremely fine towards their upper extremities ; at 

 each angle of the zigzag, a pair of short repeatedly dichot- 

 omous branches are given off, the last divisions ending in 

 sharp or spinous-like points, (f. 5.) 



The joints of the stem, as well as the joints of the branch- 

 lets, are each provided with a row of three prominent holes 



