The respiratory membrane is formed where the walls of a capillary touch the walls of an alveolus. At the respiratory membrane, gas exchange occurs freely between the air and blood through the extremely thin walls of the alveolus and capillary. Septal cells and macrophages are also found inside the alveoli.
Little or no pollen should be showing oil the actual flowers (those red or green button-like parts in the center of the colorful bracts). Be sure the plant is well wrapped when you take it outside on your trip home because exposure to low temperatures for even a short time can injure leaves and bracts. Unwrap the plant as soon as possible because the petioles (stems of the leaves and bracts) can droop and twist if the plant is left wrapped for too long. For maximum plant life, place your poinsettia near a sunny window Or Some other well-lighted areas Do not let any part of the plant touch cold window panes.
More freeze tips: 1  If freezes are forecast for several nights in a row, plants can stay covered with blankets or sheets for days without harm. 2  Where the leaves of tropical plants touch the plastic covers they will freeze. 3  To minimize leaf burn, you can lift the plastic cover to keep it off the foliage. 4  Be extra careful when using electric space ... If freezes are forecast for several nights in a row, plants can stay covered with blankets or sheets for days without harm. 2  But eventually the covers will need to be removed so the plants can get light. 3  Where the leaves of tropical plants touch the plastic covers they will freeze.