| bacteria | a unicellular microscopic organism that lacks chlorophyll and multiples by fission. |
| bacterial | a unicellular microscopic organism that lacks chlorophyll and multiples by fission. |
| bacterium | a unicellular microscopic organism that lacks chlorophyll and multiples by fission. |
| basal | pertaining to the extremity of an organ by which it is attached to its support; said of leaves when at base of plant only. See rosette. |
| biennial | of two season's duration, normally flowering, fruiting and dying the second growing season from time of seed germination. |
| blight | a disease characterized by general and rapid killing of leaves, flowers, and stems. |
| bracts | a much-reduced leaf, often scale-like and usually associated with a flower or inflorescence. |