Protococcoidece 179 



Most of the Protococcoidese multiply by simple cell-division, 

 which takes place in one, two, three, or sometimes in many 

 directions of space. 



Asexual reproduction is generally accomplished by the pro- 

 duction of one or many bici Hated zoogonidia from a mother-cell, 

 and in some families this is the sole method of reproduction. 

 There are many different types of asexual spores found in the 

 genera of the Protococcoidese. Some of these are akinetes and 

 others are aplanospores. One type, which is worthy of special 

 note, is the autospore. A number of autospores are generally 

 produced in a cell, each spore having on liberation the general 

 form and appearance of the mother-cell. In some of the ccenobic 

 forms the plants are reproduced by the formation of autocolonies. 



Most of the methods of sexual reproduction, both isogamous and 

 heterogamous, which are exhibited by the various Chlorophycese, 

 are found in the order Protococcoidese. 



The order seems to me to be best subdivided into the following 

 eight families, of which the first one is doubtfully placed in the 

 Protococcoidese as the plants included in it have certain relation- 

 ships with the Chsetophoraceae. 



Family 1. Chcetopeltidece. Unicellular or multicellular, sometimes 

 pseudoparenchymatous. Some or all of the cells furnished with hairs 

 or bristles, either simple or sheathed and often mucous. Multiplication 

 by division of cells in two directions. Reproduction by 2- or 4-ciliated 

 zoogonidia and by 2-ciliated gametes. 



Family 2. Volvocacece. Unicellular or consisting of a definite 

 coenobium of cells, which are either united by protoplasmic processes 

 or enclosed within the swollen mucous mother-cell-wall. All the cells 

 are ciliated and motile in the vegetative state. 



Family 3. Endosphceravece. Unicellular or slightly branched and 

 ccenocytic; cells solitary, generally rounded, often with button-like 

 excrescences of cellulose ; chloroplasts with numerous pyrenoids. No 

 vegetative division. Reproduction by spores, zoogonidia and gametes. 

 All the genera are endophytic. 



Family 4. Characiece. Unicellular ; cells solitary, differentiated 

 into base and apex, epiphytic on other Algse ; chloroplast parietal with 

 one pyrenoid. No vegetative division. Reproduction solely by zoo- 

 gonidia formed by successive divisions of the contents of a mother-cell. 



Family 5. Pleurococcacece. Unicellular and globular, or of short, 

 ramified, few-celled filaments, never attenuated into hairs ; often 

 pseudoparenchymatous ; chloroplasts one or several, parietal, with or 

 without pyrenoids. Multiplication by division in two or three directions, 

 and more rarely by zoogonidia. Cell- walls very firm. 



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