320 KJELLMAN, THE ALG^. OE THE ARCTIC SEA. 



Gen. CMorocliytrium Cohn. 



Biol. Pflaiiz, 1,2, p. 102. 



Chlorocliytrium Inclusum nob. 



Chl. ill statn vegetative sphfericum vel subsphaericum in planta gestatrice omnino inclusum, evolutione 

 zoosporarum iustanteJpauUulo prolongatum, depresso-conicura, ampalliefornne, ovoideum vel ellipsoideum, deiuura 

 vertice apiculato telam corticalem plantse gestatricis peuetvante nudum, ostiolo formato zoosporas emittens. Tab. 

 31, Hg. 8—17. 



Description. Tliis alga lives endophytic in Sarcophyllis arctica, being placed in 

 most cases near the surface of the nurse-plant, soinetimes in the iniddle of it (fig. 8). 

 In its vegetative state it is completely enclosed in the nurse-plant, being covered at 

 least by its cortical layer, but sometimes surrounded by its middle layer which is formed 

 of branching eell-filauients (fig. 9). It then has a spherical or abnost spherical shape, 

 80 — 100 ,«. in diameter. Its colour is yellowish green. The thin cell-wall is of equal 

 thickness. The chromatophore is thin, spread along the whole of the wall. At that 

 period when the zoospores are to be produced, the cell is elongated in the direction 

 of the nearest surface of the nurse-plant, and becomes ovoid, ellipsoidical, short cone- 

 shaped, or bottle-shaped (fig. 12 — 15). The membrane grows thicker especially at the 

 side facing outwards, and there is formed here a short cone-shaped outgrowth of cel- 

 lulosa, which contributes probably to the piercing of the cortical layer. The alga 

 assumes a more intense yellowish-green colour, the coloured plasma increases in mäss 

 and is finally divided into a large number of densely packed zoospores. As included 

 in the nurse-plant, the alga, both in its vegetative and in its fructiferous stage, pos- 

 sesses a greater or less number of different bulgings, evidently caused by the surroun- 

 ding tissue impeding its equal groAvth (fig. 9, 11, 16). The zoospores issue through 

 an opening formed by the dissolution of the cell-wall at the top of the cell beyond 

 the nurse-plant (fig. 16). As to the structure, germination and further development 

 of the zoospores I know nothing, because I have only had the opportunity of exa- 

 mining dried specimens. Those individuals which lie in the central part of the nurse- 

 plant are usually developed to a far greater size than the others. Their longest dia- 

 meter can attain even 275 ,«. Their membrane is much thickened equally. This may 

 possibly be a state of rest which is interrupted when at the dissolution of the nurse- 

 plant those individuals are liberated. I have hesitatingly referred the present alga to 

 the genus Chlorochytriwn, with the other species of which it has much in common. 

 The question as to what genus it rightly belongs to, can only be determined with cer- 

 tainty, when the history of its development shall be known. 



Habiiat. All the specimens of Sarcopliyllis edulis that I have examined, at what- 

 ever degree of longitude and latitude and whafever season of the year they have been 

 taken, have been found to contain a greater or less number of this endophyte. I have 

 found it most plentiful and most strongly developed in specimens of Sarcophyllis arc- 

 tica collected in the winter months, especially in December. It was then so numerous 

 as to be counted in hundreds in a couple of square millimeters of the surface of the 



