14 



ELEMENTARY STUDIES IN BOTANY 



illustrations of the Algse show examples of many-celled 

 individuals. 



The bodies of many-celled Algse have different forms, 

 which may be referred to three general heads. It has been 

 stated that cells divide. This is too complicated a process 

 to describe here, but in general it means that the nucleus 



FIG. 4. Nostoc (A) and Gloeotrichia 

 (B) : the colony has the form of a 

 beaded filament, imbedded in a 

 mucilage sheath ; in B the cells at 

 the base of the colony are much 

 larger than those above, showing 

 that the individual cells are be- 

 ginning to differ. 



FIG. 5. Oscillatoria : a> 

 very compact fila- 

 mentous colony, in 

 which the cells work 

 together to produce 

 the oscillating move- 

 ment of the colony. 



divides first and that a new wall is laid down between the 

 two nuclei and extends through the cytoplasm to the old wall, 

 making two cells half the size of the original one, just as 

 a partition run through a room divides it into two smaller 

 rooms. The new cells differ from the new rooms, however, 

 in growing until each one is as large as the old cell. 



