4 MORPHOLOGY 



tiply indefinitely by division. Finally these amoeboid cells begin to 

 coalesce and a plasmodium is gradually built up (fig. 3). The in- 

 dividual amoeba-Uke cells that enter into the structure of the Plas- 

 modium may lose their identity or not, but 

 their nuclei do not fuse. A plasmodium, there- 

 fore, is a mass of coalesced naked cells, each 

 represented in the complex body at least by its 

 nucleus. It would be confusing to indicate 

 Fig. 3. — A small group the variations that may occur in this life 

 of amoeboid cells, each history. It is sufficient to say that the flagel- 



contaimng a distmct nu- •' ... 



cleus, begimimg to coal- lum Stage is regularly absent m certam forms, 

 esce in the formation of and that the flagellum stage and amoeba stage 



fromir^™'"^*^*^""^ ™^y ^""^y^* repeatedly before the formation of 

 a Plasmodium. 

 In general it may be said that the structure and behavior of the nutri- 

 tive body of these organisms would seem to relate them to animals; 

 but that the reproductive structures are just as distinctly those of 

 plants. 



2. SCHIZOPHYTES 



The name of the group means "fission plants," referring to the fact 

 that the characteristic cell divisions occur in rapid succession and repre- 

 sent the only method of reproduction. The two divisions of schizo- 

 phytes are distinguished in general by the presence and absence of 

 chlorophyll, which means that one group comprises independent, food- 

 manufacturing plants, and that the other comprises parasites and 

 saprophytes (see p. 61). 



(i) Cyahophyceae 



General description. — These are the blue-green algae, as indicated 

 by the name, and very commonly they are presented as one of the groups 

 of algae. This association is made chiefly because of the presence of 

 chlorophyll, but the differences from the true algae are so important 

 that the ability to manufacture food should not outweigh them. A con- 

 sistent name for the group is Schizophyceae (fission algae), but we have 

 retained the name which is in far more common use, and which refers 

 to the most conspicuous feature of the group, narnely, the usual presence 

 of a blue pigment (phycocyanin) in addition to the green. This associa- 

 tion of chlorophyll ( ?) and phycocyanin gives to the plants, at least in 



