164 Algae. 



cells, lateral protuberances often being sent out which pass- 

 through the jelly, meet and form a pit. This pit may either 

 be an unthickened spot in the original fission walls, or the result 

 of the forcing apart of contiguous cells by the development of 

 the gelatinoLis middle lamella, leaving the cells in contact at 

 certain points. A specific investigation of these tissues in the 

 hold fast, stipe and lamina showed some slight modifications 

 from the general consideration. 



The apical cell is an epidermal cell, two or three times as- 

 large as other epidermal cells and much richer in contents. It 

 is shaped like a truncated pyramid and daughter cells are cut 

 off in succession. These divide more rapidly in plains trans- 

 verse to the axis of the lamina, thus soon grovving beyond the 

 apical cell and producing a bifurcation. 



The conceptacles are shown to originate by the cutting of^ 

 of basal cells from several contiguous epidermal cells, instead 

 of a Single cell as has been supposed. These basal cells divide 

 periclinally into six or more tiers of cells, and directly over 

 these one or more epidermal cells disintegrate. Thus begins 

 the cavity which is increased by the further decomposition of 

 other epidermal and meristematic cells. When this disintegration 

 stops a healthy surface is formed from the deeper and marginal 

 meristematic cells which give rise to paraphyses and repro- 

 ductive Organs. Both the paraphyses and reproductive organs 

 arise as buds from cells lining the conceptacle and there seems 

 to be no specialization of parts which produce these, except 

 that the antheridia sometimes do not develope as close to the 

 ostiole as the oogonia. The development of the oosphores was 

 not followed satisfactorily owing to difficulties in staining 

 specimens preserved in formalin. But four nuclei could be 

 made out in the oogonial material, and the double-Iayered 

 condition of the wall is not believed to be normal, but due to 

 the tension of dehydration and the shrinking of the gelatinous 

 middle substance upon the inner layer of the wall. 



The antheridia were found to be borne on simple pediceF 

 cells as well as branching hairs, but aside from this they 

 seemed to conform to the usual structure of these organs in 

 Fucaceae. 



The technique used in the investigation is given in some 

 detail, the stain most generally useful being fuchsin and methyF 

 violet, differentiation being controlled well by washing in acid 

 alcohol. Moore. 



Molisch, H., Amöben als Parasiten in Volvo x. (Be- 

 richte der Deutschen Botanischen Gesellschaft. Jahrg. XXI. 

 1903. p. 20—23. Taf. 111. Fig. 1—4.) 



Von Mitte bis Ende November beobachtete Verf. in den 

 rotirenden Colonien von Volvox minor Stein, die er Ende 

 September in grosser Menge im Hauptbassin des Prager bo- 



