Fig. 7
The schematic diagram about the dispersal of the sporophyll units. A The velocity-time curve of the falling model. The falling object accelerates air around downward, producing air resistance which opposes gravity. When the object reaches the ground, the velocity of object also reaches the maximum named terminal velocity \(\left({v}_{\mathrm{ter}}\right)\). The shaded area is equal to the falling height. If the falling distance large enough, the terminal velocity will converge towards the limit velocity named balanced velocity \(\left({v}_{\mathrm{bal}}\right)\). Red solid line shows the case of free fall as a contrast. B The approximate velocity–time curve of falling model in three situations. The points \({t}_{1}, {t}_{2},{t}_{3}\) on the horizontal axis represent the time when the falling distance reach 9.0 m in small Reynolds numbers, large Reynolds numbers and intermediate situation.