NOTES AND ABSTRACTS. 



519 



ful examination by every botanist who has worked on plant associations 

 or ecology. 



The country studied consists of three plains, with a soil varying 

 from sand to sandy loam, and which were the deltas of the Winooski 

 Eiver at various periods, just at its entrance into Lake Champlain. 



The country was originally forest-covered, probably with white pine 

 (Pinus Strobus?) dominant. When this was cut over, pitch pine 

 (P. rigida) became the controlling trees of the second generation, with 

 undergrowth of Myrica, Pteris, Kalmia, Vaccinium spp., Cdrex, Dier- 

 villa, Solidago, and Rubus in some cases. 



Elsewhere, on less sandy soils, Quercus velutina and Q. alba formed 

 about one-third of the pitch pine forest. 



The pitch pine was subsequently cut out, and, in consequence, 

 Myrica and Pteris became dominant, with beneath them a carpet of 

 Vaccinium. 



When periodically burnt this association becomes so dense as to 

 allow no trees to grow, and as many as 60 Myrica plants may be found 

 on a square metre. This Myrica-Pteris association, if not burnt, begins 

 to die out at 15 to 20 years old, and pitch pine establishes itself in the 

 open places. It seems probable that eventually, if unmolested by man, 

 such areas will regain their dominance of pitch pine. 



When fire is kept out from the time of clearing reafiorestation is 

 more rapid. Coppice shoots of Oak, Betula populifolia, Aspen, red 

 maple, and Amelanchier fill up the vacant spaces. W^hen the Oak 

 coppice is about 15 years old it shades out much of the under-vege- 

 tation, and the pines begin slowly to re-establish themselves. Pitch 

 pine enters more slowly than the white pine, which endures shade 

 better. 



White pine reproduces readily on clean-cut areas where the white 

 birch is dominant. The latter tree persists only for 20 to 30 years 

 in competition with oaks and pines. 



On abandoned cultivated fields trees may (1) at once begin to esta- 

 blish themselves, as when a ploughed field near mature trees is aban- 

 doned in a heavy seed year. In other cases (2) there is a preliminary 

 herbaceous stage, but the grasses never obtain complete control so as 

 to form sods. (3) Areas cropped for grass or pastured for a longer or 

 shorter time, and then abandoned, pass through a sod-forming stage. 



Of the succession (1) examples of seeding by white birch and pitch 

 pine are given. As regards (2) the fields are at first occupied by weeds, 

 such as Setaria and Erigeron canadensis, which may continue for four 

 years. Later Oenothera biennis, Sheep's sorrel, Antennaria, &c., 

 come in, with scattered groups of Cyperus, Carex, and grasses such as 

 Danthonia and Andropogon. Mosses (Polytrichum) appear in sterile 

 places, often covering one-third of the area. These patches of Poly- 

 trichum are ideal germinating beds for pitch pine, white pine, and white 

 birch. Usually Myrica precedes the tree invasion. The rapidity of 

 afforestation depends on the proximity of mature seeding trees. 



In the third case, when the fields were seeded down and bore crops 



