Because the foliage acts as a screen, which prevents the radiated heat of the earth from passing away.
352. Why is there no dew formed on windy nights?
Because, as winds generally consist of dry air, they absorb and bear away the atmospheric moisture.
353. Why are valleys and low places chiefly subject to dew?
Because the elevated lands around them prevent the disturbance of the air in which the moisture is held.
354. What bodies are most likely to be covered with dew?
All bodies that are good radiators of heat, such as wool, swansdown, grass, leaves of plants, wood, &c.
355. What bodies are likely to receive little dew?
All bad radiators of heat, such as polished metal surfaces, smooth stones, and polished surfaces generally. Dew will be found to lie more abundantly upon rough and woolly leaves than upon smooth ones.
356. At what period of the night is the largest amount of dew usually formed?