502 EXPLANATION OF THE PLATES. 



rata L,, var. lacustris. They lie in one of the reticular 

 circulation-filaments, upon the wall, and have become 

 parenchymatous, from their crowded position. Some (a) 

 contain only homogeneous chlorophyll. Others possess, 

 in addition, a small or large starch-granule, which is 

 coloured blue by the action of iodine. 



14. Starch-utricles (starch-granules) from the corm of 

 Crocus vernus Willd. They have an angular form. 

 Iodine has coloured the starch-layers blue, but not affected 

 the original membrane. Diam. = '004 of a line. 



15. Starch-utricles (starch-granules) from the peduncles 

 of Vitis vitifera, with very evident membrane and large 

 cavity. The starch-layers have become coloured blue by 

 iodine ; the original membrane remains uncoloured. 



16. Chlorophyll-utricles, from a cell of Conferva glome- 

 rata L. var. marina. They lie in rows in the parietal 

 circulatory reticulation, and have expanded lengthways 

 in the direction of the current. The utricles lying in 

 the angles of the network exhibit elongated processes 

 toward the lines of the net. In each utricle lies a starch- 

 granule. 



17. Chlorophyll-utricles, from Nitetta, with a colour- 

 less membrane and homogeneous contents, and with from 

 two (a) to five (b) starch-granules. 



18. Mucilage-utricles from Nitetta. 



a. With homogeneous mucilage and smooth membrane. 



b. The mucilaginous contents have become agglome- 

 rated into a ball, and separated from the wall on one 

 side ; the membrane is punctated outside. 



c. As in b, the surface is clothed with minute spines. 



d. The spines have disappeared ; the surface is ir- 

 regularly uneven. 



e. A piece of a spinated membrane more highly 

 magnified. 



