I'll I'. II <H; \ < M NEBB U5K \. 



4. lot <>l rich i.i pi sum (AG.) THUEET I.e. 

 Rivularia pisum Ag. Syst. Alg. 25. L824. 



Masses soft, spherical, '. mm. 5 mm., aeruginous or olive-green; filaments 

 elongated; lower cells with a distinct sheath, once to twice as loi 

 broad, the cell-contents aeruginous, upper celte Longer with in.listiu.-i 

 sheaths; sheaths close, simple; spores cylindrical, often several times the 

 diameter in length, heterocysl usually wider than the vegetative cells, 

 7 11'/ in diam.; the spores 6 12/*. 

 On water plants, Minden. PI. III., Pig. 33. 



2. ISACTIS Thubet Ann. Sci. Nat. Bot. 6, I.. 382. L875. 



Filaments agglutinated by a more or Less firm cilage, often Lncrusted \\ it h 



lime, forming a flat strain in, erect, parallel, attached at the base; spores 



formed in the lower part of the filament. 

 Etymology: Greek taog, equal, an I am . ray. 



Isactis fluviatilis (Kuetz) Kirch. 



Euactis rivularis fluviatilis Kuetz, Sp. Alg. 342. 1849. 

 Zonotrichia fluviatilis Rabh. Fl. Eur. Alg. II.. 21 1. L865. 



Stratum often extended with a more or less calcareous crust, usually olivace 

 ous, brown, or reddish; filaments !) 12// in diam . closely compacte I and 

 sometimes apjiarently one stratum above another, the end- sudden lj 

 acuminate; cell light aeruginous, sheath close, colorless to brownish, 

 widened at the end and til nil lose; heterocysl colorless, globose. 

 Minden. PI. Ill, Fig. 31. 



Family.— BACTERIACEAE. * 



Minute fungi without mycelium, typically unicellular, or at Leasl the divisions not 

 visible except at the time of the absection of new cells; cells of very diverse form round. 

 elliptical, bacillar, or filamentous), generally surrounded by a gelatinous envelope. one 

 or both ends often provided with 1-3 flagella; growth peripheral, never apical; sexual !■•■ 

 production undeveloped; asexual reproduction by simple division or by B] 

 spores or arthrospores). 



The bacteria are either saprophytes or parasites in vegetabli or animal tissuea 

 The former may be simple saprophytes {Bacterium terrno, Spirillum 

 undula), or zymogenic forms (Bacterium aceti, B. pasteurianum). 

 sitic or pathogenous bacteria cause various diseases of plan's and ani- 

 mals, as apple blighl (Micrococcus amylovorus), sorghum blighl Bacillus 

 sorghi), diphtheria (Micrococcus diphtheriticu 

 Bacteria are either motile or non-motile. Motile forms are provided with 

 one or more flagella, or, as in Rasmusst nia, possess tic power of oscillal ion 

 which is still more highly developed in the Oscill llany 



forms appear to move about very rapidly in cult ure solutions, hut this is 

 nothing more than the Brownian movement characteristic of all minute 

 particles suspended in liquids, [nadditionto the non-motile I 

 teria, motile forms when they enter the zoogloea 



of movement. Here, too, however, a distinction must be made between a 

 true zoogloea and a Loosely aggregated colony of actively moving in- 

 dividuals. 



By Frederick B. Clements. B. Sc. 



