7. Heterochronous culture of Helianthus annuus and Datura stramonium. One hundred seeds of Helianthus were scattered over one half, and the same number of Datura seeds over the other half of the plot. In both, also, 50 seeds were sown in one 4–inch circle, and 25 seeds in a second circle at some distance. A month later, 100 seeds of Helianthus were sown in the Datura plot, and vice versa.
8. Family culture of Helianthus, Kuhnia, Panicum, Bidens, Onagra, Datura, Penthorum, Solidago and Verbascum. The plot was divided into 9 squares and in each were sown 50 seeds of one of these plants.
9. Community culture. The sowing was made exactly as for the family culture, except that 20 seeds of each plant were used. In the middle of each square, 5 seeds of a different species were planted. For the Helianthus, Kuhnia, and Panicum groups, Onagra was used; for Bidens, Onagra, and Datura, Helianthus was used, and for Penthorum, Solidago, and Verbascum, Panicum.
At the time the cultures were started, check plants were sown in pots. The most vigorous seedlings were transplanted singly to large pots, and grown under conditions of water, light, and soil as similar as possible to those of the competition plots. Photographs of check plants and plots were made at the proper intervals, and the plots were charted in quadrats to show the course of competition. The factors which control competition were sought in a critical study of water-content and light values, which is still in process. This work has gone far enough to indicate the correctness of the view[[45]] that competition is purely physical in character. It has, moreover, been demonstrated that “room” in competition is merely a loose expression for the relation between the number of individuals in a given space, and the amount of water, light, and temperature available in the same space.
GLOSSARY
Note: Last terms frequent in compounds are found in their proper place alphabetically. The accent is indicated only in those words accented on the penult; all others are accented on the antepenult, or recessively.
abundance, the total number of individuals in an area.
acospore (ἀκή, point), a plant with awned disseminules.
acrophyti´um (ἄκρον, peak), an alpine plant formation.
acti´um (ἀκτή, rocky coast), a rocky seashore formation; actad, plant of a rocky seashore.