224 Pennington — A Chemico-Physiological 



number of short, almost square cells, while the uniting 

 thread is formed of cells of the normal length. These 

 short cells may alternate with long ones in the same thread, 

 where they generally occur in chains of three or four. As 

 we find Spirogyra to be strictly monoecious there are, of 

 course, a number of cells which remain unfertilized. 



These stimulated cells, which are unable to conjugate, 

 accumulate the large amount of tannin and retain it. 

 Indeed, proportionately to their size, the amount of tannin 

 stored by them is much greater than in the larger cells. 

 Frequently these cells form rudimentary or even fully de- 

 veloped tubes, which, however, never meet a corresponding 

 tube. 



We may ask, does not this tannin behavior approximate 

 to that of malic acid in the fern ? The tannin, though a 

 constant constituent of the plant, is formed in much larger 

 quantity immediately preceding conjugation. During the 

 first period of attraction between the cells, it maintains 

 this quantity, but as the cells are drawn closer and closer 

 together we find it disappearing and apparently by way of 

 the tube, since it is there that we detect its last traces. 

 The evidence indicates that it diffuses through the cellulose 

 wall of the tube, and this may account for the fact that we 

 have so marked an alteration in the wall of the cell at this 

 period. (The modification of the cell wall will be again 

 mentioned.) It seems scarcely likely that the tannin 

 formed should act as a food supply. 



The presence of a resin so closely united with the 

 chlorophyll would indicate a like origin for this substance. 

 Though the plant synthesis of both classes of compounds 

 is as yet unexplained, the indications are that the tannins 

 are intermediate between the oils and resins. For the 

 pines, at least, it has been established that the young cells 

 are filled with protoplasm, which is partially replaced later 

 by tannin. Then oleo-resins appear, and increase at the 

 expense of the tannin and the protoplasm. According to 

 this view we would expect the resin content of the cells 



