16 Mr. G. H. K. Thwaites on the Cell-Membrane of Plants. 



some plants, belonging to the family Oscillatoriece, in one of which 

 (a species of Spirulina) there appears to be no real membrane — 

 the plant consisting of a mucous matrix, out of which, when the 

 species is mature, emerge oscillating spiral filaments, which from 

 their exhibiting no trace of cell-membrane, or even of any divi- 

 sion, by septa, into separate portions, and from the rapidity with 

 which they become decomposed, I believe to be continuous masses 

 of endochrome held together by mucus. Another species to which 

 I would direct attention is the Lyngbya ferruginea, Agardh, a 

 plant scarcely differing from Oscillatoria, except in the greater 

 firmness of the membranous sheath which invests each filament : 

 the filaments of this plant are composed of lenticular masses of 

 endochrome, and during the early part of their growth are in- 

 closed in a membranous sheath ; from this, however, they emerge 

 when mature, and soon afterwards become broken up into the 

 separate masses of endochrome, each of which appears to be held 

 together by a kind of mucus, and not to be surrounded by a cell- 

 membrane. I am inclined to believe that the Oscillatoriece generally 

 have no real cell-membrane, unless the common sheath, investing 

 each filament, be considered as such. In Microcoleus, one of the 

 same family, the filaments are invested with a mucous or gelati- 

 nous, not membranous sheath ; proving that the membranous 

 sheath which incloses the filaments of the above-named Lyngbya 

 is not to be viewed in the light of the ordinary cell-membrane, 

 though its functions are probably identical with it. 



When treating of such objects as the foregoing, I am aware of 

 the danger of advancing a negative proposition ; of stating that 

 certain structures do not exist, when an improved method of ob- 

 servation may eventually discover their presence : I would there- 

 fore request that what has been just advanced may be considered 

 as what I firmly believe to be the case, and not as an absolute 

 indisputable certainty. But the doctrine I would advance does 

 not rest solely upon the possibility of proving the absence of cell- 

 membrane in a perfect organism ; though it would naturally de- 

 rive weight and probability from such a source. 



I now proceed to point out instances in which the cell-mem- 

 brane is seen to be of quite a secondary character ; and that its 

 development is regulated entirely by the condition of the endo- 

 chrome it contains, and that, in fact, it owes its existence to this 

 endochrome. The production of cell-membrane and endochrome 

 has the appearance frequently of being synchronous, but the en- 

 dochrome may sometimes be seen becoming invested with a cell- 

 membrane, and this may be well-observed during the formation 

 of the spore of Zygnema and other species of Conjugatece. Those 

 who have paid attention to this family of plants are well aware, 

 that previously to the formation of the fruit, two cells unite by 



