THE S TUD Y OF AL GAi IN HIGH SCHOOLS. 6i 



duces in a manner similar to Oscillatoria, and also in a second way. 

 Some of the ordinary segments become swollen, acquire a thicker 

 wall and granular contents. They are then spores, and separating from 

 of the filament, undergo a period of rest at the bottom of the pool, 

 after which they are capable of growing into young Nostoc plants. 



CHLOROPHYCEiE, or Green Algae.— Plants unicellular or 

 multicellular; plant body spherical, filamentous, expanded, saccate, 

 foliaceous, or possessing stem and leaf (branched or unbranched) ; 

 chlorophyll generally present in chromatophores of definite form ; 

 reproduction by zoogonidia, by union of gametes, or by fecundation 

 of Q.^'g by spermatozoid. 



These are the Alga most commonly met with in inland waters. 

 Some Algse are also marine. Common names which well describe 

 them are pond-scum, water silk, green slime, green felt, water flannel, 

 water net, bass-weed, etc. Ordinarily they form tufts or tangled 

 masses of green threads. 



Spirogyra. (Greek speira, a coil and gyros, a circle). 



Pond-scum, as the name indicates, forms a slippery, light green 

 mass of threads floating on the surface of pools, slow-running streams 

 and lakes. When of this color and appearance one need not ex- 

 pect to find fruit. In the fruiting condition, which is common in 

 August and September, the mass is apt to be of a dirty brown color, 

 not inviting in appearance. Nevertheless, it is extremely interesting 

 when seen under the microscope. It seems unnecessary, however, to 

 farther describe this plant, since its life-history is thoroughly dis- 

 cussed in all botanical text-books and illustrations are plentiful. 



Protococcus. [Greek prot OS, first, diniS. kokkos, a berry). 



Great numbers of these unicellular plants growing in heaps or 

 masses, form the green coating so often seen on damp flower-pots, 

 stone walls, on the sides of brick buildings, on damp tree-trunks and 

 similar places wherever there is moisture and light. Under the 

 microscope one sees tiny spherical green cells, each one of which is a 

 plant. Sometimes the green contents of such a cell may be seen 

 dividing into several roundish bodies — zoogonidia. These break 

 through the cell wall and swim about for a time. Finally they come 

 to rest and develop into new individuals. 



Draparnaudia. (Named from a French botanist, Draparnaud). 



This plant forms gelatinous, attached green tufts in cold spring 

 waters and indicates that the water is pure. The microscope shows 

 the plants to consist of a main stem with numerous branches. The 



