PLATE IIL 



PROTOCOCCUS. 



PROTOCOCCUS VULGAEIS, the green scum on the bark of trees (Gr. protos, first ; kokkos, a berry). 

 Fid. 1. Showing 



f Cell-wall or sac. 

 A CELL -c Protoplasm containing green, sometimes red, chlorophyll (Gr. chloros, green ; phyllun, a 



( leaf). 

 FIG. 2. EFFECT OF 



. Iodine Protoplasm stained and nucleus brought out. 



b. Iodine and sulphuric acid The cell-wall becomes blue and the protoplasm coagulates. The 

 sulphuric acid converts cellulose into starch, and the iodine with starch forms the blue iodide 

 of starch. 



e. Crushing causes rupture, and shows that the cell-wall is tough and resisting, while the proto- 

 plasmic contents are semi-fluid. 



d. Potash (KHO) dissolves out the protoplasmic contents. 

 FJG. 3. Showing MULTIPLICATION BY DIVISION 



a. Division into two. 



b. Division into four. 



This process is the same as that which goes on at the growing point in the higher plants 



(See Chara, fig. 4.) 

 FIG. 4. Showing MULTIPLICATION BY ENDOGENOUS DIVISION AND PRODUCTION OF MOTILE FORMS 



a. The protoplasm has gathered itself up into a number of round masses, each of which is a 



zoospore or zoogonidium (Gr. zoos, alive ; gune, seed). 



b. A zoospore that has escaped from the parent cell. It consists of a naked mass of protoplasm, 



with two long vibratile protoplasmic threads or cilia by which it moves about. 



PROTOCOCCUS PLUVIALIS, found in water-butts (L. pluvia, rain). 



( Cell-wall. 

 FIG. 1. RESTING FORM < Protoplasm. 



( Chlorophyll grains. 

 FIG. 2. PREPARATION FOE DIVISION. 

 FIG. 3. Showing RESULT OF DIVISION. 

 FIG. 4. MOTILE FORMS ZOOSPORES OR ZOOGONIDIA 



a. The protoplasm has drawn itself away from the cell-wall at all but two points. At these 



points two vibratile cilia protrude through the cell-wall. 

 1>. A naked zoospore. 

 FIG. 5. EREMOSPHJSRA VIRIDIS, a close ally of Protococcus, containing starch granules 



a. Unstained. 



b. Stained with iodine to bring out the starch granules. 



No starch is found in the Protococcus itself, probably because it uses up the starch as fast 

 as it is manufactured. 



DIAGRAM OF PHYSIOLOGY 



a $ b. Show that in the dark no oxygen is evolved from carbonic acid (C0j). 



a r. Show that in the light the carbonic acid is absorbed and oxygen gas given off. 



This process, viz. the absorption of COz and evolution of 0, is called Assimilation. 

 Respiration is quite a different process ; it consists in the absorption of O and the evolution of 

 COj. In the green plant these two processes go on together. 



