ALGAE 



105 



the causes of local eruptions, such as boils, ulcers, gangrene, etc. Bacillus 

 typhi in the digestive tract causes acute inflammation — typhoid fever. 

 Bacillus pneumoniae and the B. diphtheriae on the mucous epithelium of 

 the pharynx and adjacent cavities, and B. tuberculosis in the lungs and 

 on other serous membranes of the body are well known. B. tetani in 

 the blood is the cause of lock-jaw. B. anthracis causes a disease fatal to 

 cattle and occasionally to man. Asiatic cholera, leprosy and many dis- 

 eases of domestic animals, such as chicken cholera, foot rot, black leg, etc., 

 are bacterial. 



232. Order 2. CyanophycecB {SchizophycecB). — The Cyanophyceae are also 

 called blue-green algae because of the presence of a blue pigment (Phyco- 

 cyanin) in addition to chlorophyll. These plants are found only in water 

 or on moist surfaces. They multiply by fission like the bacteria and the 

 cells adhere in threads or are enclosed in masses of jelly formed by the 

 swollen cell membranes. The nucleus usually consists of scattered 

 chromatin granules. 



233. Class 3. Diatomeae. — The Diatoms are a large group. 

 They are also unicellular and the cells separate completely 

 though they may adhere in chains or be attached by a common 

 stalk. The cells are usually bilaterally symmetrical and the 

 cell wall consists of a silicious capsule of two parts which lit 

 into each other. The surface of the capsule is often very 

 elaborately ornamented. There is a single central nucleus 

 and one or more large lobed chromatophores containing a 

 brownish-yellow pigment in addition to a substance similar 

 to chlorophyll. Multiplication takes place asexually by fission 

 and also by conjugation. 



234. Class 4. Conjugatae. — The ConjugatcT are unicellular, 

 though the cells may be connected in filaments. The cell has 

 a single nucleus, one or more chlorophyll green chroma lo})hores 

 of a complicated form and one or more pyrenoids. Sexual 

 reproduction through the union of two non-motile gametes 

 (conjugation) to form a zygospore, is characteristic of the group. 



235. Order i. — The Desmidiacece are single cells which consist of two 

 symmetrical halves often joined by a narrower portion like a dumb-bell, 

 the cells are frequently very bizarre in form. The nucleus lies in the 



