PLATE IIL 



PROTOCOCCUS. 



PEOTOCOCCUS VULGARIS, the green scum on the bark of trees ((Jr. protos, first ; IwkJms, a berry). 

 I'lG. L Showing — 



f Cell-wall or sac. 

 A Cell -; Protoplasm contaming green, sometimes rod, chlorophyll (Gr. cldoros, green ; xjIujUuu, a 

 ( leaf). 



Fig. 2. Effkut 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. 



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



plasmic contents are semi-fluid. 



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

 Fju. 3. Showing Multiplication by Division — • 



a. Division into two. 

 h. 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.) 

 Fio. -1. Showing Multiplication by Endogenous Division and Peoduction of I\foTiLE Foems — 



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



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

 h. 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. 



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

 ( Cell-wall. 

 Fig. 1. Eesung Fokm ■; Protoplasm. 



( Chlorophyll grains. 

 Fig. 2. Preparation foe Division. 

 Fig. 3. Showing Kesult of Division. 

 Fig. 4. !Motile Forms — Zoospoees 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. 

 h, A naked zoospore. 

 Fiu. 5. Eremosph^ea Vieidis, a close ally of Protococcus, containing starch granules — 

 ". Unstained. 

 h. 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 4' b. Show that in the dark no oxygen is evolved from carbonic acid (COo). 



a «5" c. Show that in the light the carbonic acid is absorbed and oxygen gas given off. 



This process, viz. the absorption of CO3 and evolution of 0, is called Assimilation. 

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

 CO2. In the green plant these two processes go on together. 



