No. 46o.] STUDIES ON PLANT CELL.~V. 221 



recent short paper by Michniewicz (: 04) describes clearly the 

 plasmodesmen in Lupinus, especially in their relation to masses 

 of intercellular protoplasm which are discussed at the end of 

 this portion of the section. 



It is not clear whether all protoplasmic connections may be 

 considered in the same class, as Strasburger would have us 

 believe, or whether there may not be some confusion between 

 the broader cell connections which are especially conspicuous in 

 the thallophytes and certain tissues (sieve-tubes, laticiferous 

 vessels), and the delicate protoplasmic fibrils (plasmodesmen) so 

 general throughout all tissues of higher plants. As is well 

 known, the cells in actively growing regions of the red algae are 

 connected by broad strands of protoplasm that are obviously 

 left by the cleavage furrow which constricts the protoplasm of 

 daughter cells but does not entirely separate them. These open- 

 ings may become partially blocked in older portions of the plant 

 by the deposition of material so that the connections are finally 

 fibrillar but they frequently remain open for long periods, par- 

 ticularly in regions where the nutritive processes are active as 

 during the development of cystocarps. At this time new 

 fusions may be developed between neighboring cells (auxiliary 

 cells) so that they become connected in an elaborate network 

 around the cells or filaments (sporophytic) that develop the car- 

 pospores (Fig. 16, d). The Phaeophycese also furnish frequent 

 illustrations of connecting fibrils especially in the Fucales and 

 Laminariales where the cells of internal filaments are sometimes 

 connected by conspicuous strands. Certain elongated filaments 

 which traverse the central region of the larger brown algae show 

 a complicated group of fibrils that strikingly resembles the pro- 

 toplasmic connections piercing the sieve-plates of higher plants. 

 Broad protoplasmic connections are conspicuous between the 

 cells of some of the filamentous Cyanophyceae (Stigonema, 

 Tolypothrix) and in the Chlorophyceae have been reported for 

 some species of Cladophora (Kohl, : 02 ; Fig. 16, e) and for 

 Chaetopeltis, one of the Mycoideae. They do not seem to be 

 present in the Conjugales as was at first reported by Kohl 

 ('91) whose cells show a great degree of physiological inde- 

 pendence. In Volvox, studied by Meyer ('96-), each cell of the 



