FritsfU, Studies 011 Cyauopli yceae. 19i> 



corpo protoplasmatico"), and the same conclusioii is arrived at in 

 the case of OscWaria. Mnch the same view is lield by Born et 

 and Flaliault in tlieir „Revision diQs Nostocaa'e.s heterocvstees*^ 

 (86), where tlie protoplasm of tlie cell is considered to bc in 

 direct contact witli the sheath. Mnch tho niost important con- 

 tribution on the subject is Gromont's ..Recherches sur les enve- 

 loppes colhilaires des Xostocaci'e-s hlamenteuses", based on the 

 exaniination of 11 genera. Whilst a large part of the paper is 

 concerned with tho sheath, the conclnsions arrived at with regard 

 to the imniediate envelope of the cell are summarised by Gomont 

 as foUows: „La membrane propre de la cellule est toujours 

 mince. etroitement appliquee contre le j^b^^nia, mais eile jicut 

 etre cependant mise en evidence par la dissolution et la con- 

 traction de celui-ci; eile est insolnble dans les acides et ne se 

 eolore jamais en bleu par les reactifs iodes". Gomont thus 

 considers that a definite membrane is present in all cases and 

 this view is also adopted by Kirchner (98, p. 46). I refrain 

 froni citing further literature. as Gomont has done so fully up 

 to the time of liis publicatioji. 



On the grounds of my investigations 1 have come to the 

 conclusion. that each protoplast in the Cyaiiophyceae is provided 

 with two Investments of its own in the mature condition inde- 

 pendently of the externai niucilaginous sheath: the inner of these 

 investments fornis an actual membrane right round the proto- 

 plast, whereas the outer takes the form of a small cyhndrical 

 sheath enveloping the cell. These will be described more fully 

 in the course of the detailed consideration of the genera and I wisli 

 at this point only to make a few remarks on the nature of the 

 inner investment, which corresponds to the cell-membrane of 

 the two observers just mentioned. 1 have already mentioned 

 above that it is difticult to distinguish the imniediate envelope 

 of the (Jyanoplnjccous: cell in many cases; this however only 

 applies to the lateral portion of this envelf)pe. for adjacent cells 

 are separated from one another in Änabariia lor xVo.y/oci by a 

 well-marked colourless patch, representing the transverse septum. 

 but the limits of this latter with reference to the protoplast are 

 mostly dif heult to detine. Gomont (88, p. 209) suc(;essfully 

 devised a method, by which the cell-wall of Cyaiioplnicfnc could 

 be rendered evident inid by means of which he attained the 

 above-mentioned resiüts : he employed a 33 "o Solution of chromic 

 acid, which in the course of an Jiour or so dissolves away the 

 greater part of the ])rot(>]jIasmic contcnts, leaving the cell-mem- 

 l)rane perfe(^tly intact. ahhough a slight contraction scems to 

 me to be involved. Here tlierefore wd meet with a second 

 peculiarity of the cell-wall of the blue-green Algae, viz. its 

 resistance to strong oxidising agents; in this respect it differs 

 verv markcdly from iiiost otlio- ])lnnt-membranes ^). According 



ij Afconliuf:: to Gomont (Joe. cit. p. 212) similar reactions are showii 

 by the menihranes of some other Alp^ae (e. ff. a rrotoioccus . a Conferva, 

 und a Cladop/tora): these ineinhianes are huwever quite diffeieiit physically. 



