176 Dr. Hooker' 1 s Flora Antarctica. 



bulk or tenacity, after a certain period ; whilst the growing di- 

 mensions of the floating portion are increasing the difference be- 

 tween the specific gravity of the vegetable and the element it in- 

 habits, and consequently augmenting the strain upon the slen- 

 der stem by which it is attached. At some period or other, the 

 resistance is overcome and the floating part detached from the 

 submerged; though at what epoch this may take place, or wheth- 

 er it be coincident with other phases in the life of the plant, is 

 beyond our conjecture. 



u The fact that fructification is produced only on the submerged 

 young bladderless and small frond, within a few inches of the 

 very root, is highly remarkable. What then is the function of 

 the floating mass of the plant ? to one of whose thousand leaves, 

 each four to six feet long, the fructifying bears an inconceiv- 

 ably small proportion. Were this a pheenogamic plant, we should 

 recognize, in such foliaceous expansions, organs which fulfil 

 a respiratory and digestive office and are subservient and ne- 

 cessary to the development of the more important parts of the 



vegetable ; 



depend 



easily traced. As in Lessonia the multiplication of the leaves is 

 intimately connected with the development in diameter of the 

 stem, so in Mdcrosystis the development of fructifying fronds 

 may take place only at the root of the barren ones, on whose 

 previous existence they may be dependent for their origin. These 

 are, however, questions which propose themselves to us in the 



closet only, when the prospect of solving them is gone by ; and 



when they but add to the thousand regrets over lost opportuni- 

 ties, the remembrance of which weighs so heavily on the mind 

 of every naturalist, that the brightest prospects of discovery in 

 the fair future can never obliterate them." 



The general remarks of our author upon the distribution, econ- 

 omy and functions of the Antarctic Diatomacese are so just and 

 so full of scientific interest, that we deem it our duty to afford 

 them a wider circulation among our American readers, very few 

 of whom, probably, will ever see them in the original work. 



That the Diatomaceae belong to the vegetable, and not to the 

 animal kingdom, has of late years seemed altogether the most 

 probable opinion ; and this idea has recently been unequivocally 

 confirmed by Mr. Thwaites, who has most successfully investiga- 

 ted this tribe in England, and who has had the good fortune to 

 discover several species congregating, in the manner of the Zyg- 

 nemata, a fact which leaves no doubt of their vegetable nature. 



That Volvox, also, is a vegetable, would hardly be doubted, ex- 

 cept for its active movements, which, being at some period com- 

 mon to the spores of every tribe of Algae, cease to furnish a cri- 

 terion. We learn that Prof. Braun of Carlsruhe, has recently 

 studied the development of Vol vox, and has clearly demonstrated 



