PALEOBOTANY 
ing into inland lakes or into the ocean. In addition to 
rock-sediment eroded from the surface of the land, streams 
FIG. 412. Diagram illustrating the gradual filling up of lakes by the 
encroachment of vegetation, and also the stages in the origin of peat and 
marl deposits in lakes. The several plant associations of the Bog series, 
displacing one another, belong to the following major groups: (i) O. W., 
open water succession; (2) M., marginal succession; (3) S., shore succes- 
sion; (4) B., bog succession, comprising the bog-meadow (Bm), bog-shrub 
(Bs) and bog-forest (BJ); and (5) M. P., mesophytic forest succession 
(Cf. Fig. 411.) 
also transport quantities of plant (and animals) frag- 
ments, leaves, stems, pieces of bark, fruit, flowers, pollen 
and spores, roots, and even entire plants. These natur- 
