44 



protoplasm, we can cause the rapid passage of those masses through 

 the cellulose layer of the cell wall; for we cannot well believe that 

 in the very short time during which this passage is completed, a 

 transformation of a portion of the cell wall into mucilage has taken 

 place. As another proof for the direct passage of the mucilage 

 through the wall must be considered the absence of any swelling 

 or striation of the cellulose layer after the rupture of the sac and 

 while the mucilage in the hair continues to diminish and disappear. 

 We may, therefore, assume that the increasing turgor inside of the 

 hair forces the mucilage through the surrounding protoplasm and 



through the cellulose layer of the w^all. 



If, finally, we ask ourselves of what possible use the mucilage 

 might be to Brasenia^ we can only suppose that it must serve 

 the plant as a protection against the attacks of water animals 

 which are prevented by its slippery and yielding, but at the same 

 time firm consistency, to crawl on its surface and to eat the tender 

 growing parts. Moreover, the numerous kinds of larger water m 

 Algae cannot attach themselves to the growing stems and 

 buds, although, as mentioned before, Bacteria and also Diatoms 

 seem to thrive in the mucilage. 



In the intercellular air-canals we often meet with projecting 

 hair-like structures. Sometimes they are simply slight protuber- 

 ances from the cells lining the canal, but usually they are large 

 outgrowths of those cells, of a cylindrical, sac-like shape, or they 

 are inflated and widening from the base toward the rounded end 

 (Figs. 5, 6, 7), The interior is most commonly continuous, but 

 occasionally one to three cross-partitions may be noticed. These 

 hairs are often found in groups of three or four, seldom singly 

 (Fig. 7)» but most frequently occurring in large numbers, all 

 around the canal, pressing against one another and, at some 

 points, effectually closing the entire cavity. For a considerable 

 but varying distance from such a point many cells bordering 

 upon the canal send such outgrowths into the open space, dimin- 

 ishing in number as the distance increases, and the interstices 

 between them are usually filled with mucilage (Fig. 5). 



A hning of mucilage of varying thickness is also found in 

 such parts of the canal where there are only a few hairs or none 

 at all (Fig. 5. mu, upper canal). The lining does not always 



