Depth of growth. Regions of light. 
1. Bright light region, or photic region. 
a.. Macrophytes. 
b. Microphytes with photosynthesis. 
2. Dimly lighted region, or dysphotic region.. 
a. Mscrophytes stunted or fail. 
b. Few photosynthetic microphytes, ex., diatoms. 
Dark region, or aphotic region. 
Organisms not capable of photosynthesis, ex., bac- 
hewtas 
Gulf of Naples bacteria found 800-3,500 ft. 
Relation to substratum. 
(Note on Schimper’s use of Benthos, and the use of piank- 
ton and hemiplankton.) 3 
1. Benthos fixed ( Bevos depths). 
2. Plankton. 
3. Hemiplankton. 
Effect of the water on vegetation. 
I. Vegetation dependent on varying degree of salinity. 
(1) Evaporation. 
eee 2 eres water 
Zee Gtedtesr salt content tomund im the Red Seay (4.3) per 
cent. ) 
Color due to Trichodesmium. 
mae Ocean 2.5 pen cent. mineral, 2.6: per cent. salt. Greater 
in tropical than in Arctic regions. 
4. Movement of water affects the distribution of plants. 
2 SINISE NIA, 
b. Ebb and flowstide. 
Marlponds. Affected by quantity of calcium carbonate (fresh 
water marlponds). 
Inland lakes and salt ponds. 
Vegetation of hot springs. 
a. Beggiatoa. 
b. Phormidium, Spirulina. 
c. Anabaena, Gloeocapsa. 
Affected by temperature. 
1. Perennial pelagic algae no rest, some growth during 
winter. 
53 
