DEVELOPMENT AND FUNCTIONS OP CELLS. 49 



a diagram illustrating the development of a monocotyledonous 

 plant by superposed phytons ; a — <j, the successive phytons. 

 Sometimes the lower phytons develop adventitious roots from 

 the side of the stem, as represented at h, which roots are in- 

 tended to act as props or mechanical supports. This is well 

 seen in the lower joints of the stem of the Zea Mays, Indian 

 corn. Now- these buds or phytons, although capable of 

 growing independently, remain through life united to the 

 parent stem on which they develop and form by their united 

 growth the individual tree. In like manner, when plant-ceUs 

 unite together in a linear series to form the individual plant 

 called the bread-mould, each plant-cell in the series is capable 

 of propagating the species when separated from the others 

 (which it actually does, as we have already seen, when this 

 separation takes place naturally), and each plant-cell is also 

 only a repetition of the same process of growth which took 

 place in the development of the primary plant-cell. The 

 bread-mould is therefore a composite plant formed by the 

 union of plant-cells, each of which is capable of forming the 

 germ of an independent existence, and of propagating the 

 species, although it remains through life in union with the 

 parent plant-cell forming the individual bread-mould, just as 

 the permanent union and development of a superposed series 

 of phytons form the individual tree. 



56. It is therefore clear that the little bread-mould which 

 nature constructs from decaying organic matter in a few short 

 hours, consisting of a few united vegetative cells and a single 

 terminal reproductive cell, is only a simpler expression of the 

 same law which operates in the production of the forest-tree. 

 5 



