CHAPTER VI. 



TISSUES. 

 I. THE VARIOUS AGGREGATIONS OP CELLS. 



In the organisms which compose the vegetable kingdom 

 cells are found principally under the following conditions of 

 aggregation : 



92. (1.) Single Cells. A large number of the lower 

 plants, during all or a considerable part of their existence, 

 are composed of single cells They may be round, as in 

 Saceharwnyces and Protococcus, or elongated or even filiform, 

 as in certain Bacteria. It is only in the lowest groups that 



f*- JVJiMgriMi grfm*lat>a. A. the youw- cells ?n their motile rtatp en- 

 *a in the membrane of the mother-cell B, the young cells beginning to mnc 

 themselves in a cell-family. C. the cell-family fully developed.- After Braun. 



adult plants are composed of single cells, but it is an 

 embryonic condition of all others. 



93. (2.) Families, or Spurious Tissues. There are 

 some oases in which cells which are at first distinct after- 

 wards become united more or less closely into a common 

 mass, vhich may be denominated a Cell-Family, or Spurious 

 Tissue. 



(a) Pediaitrum and Hydrodietyon furnish the best examples of true 



