Figure 2.

Developmental stages of Douglas fir megagametophytes against time, emphasizing the period of Megastigmus spermotrophus oviposition. Shading indicates period of insect oviposition. The length of line indicates the range in length of stage. Stages are according to standard description (Allen & Owens 1972) of unparasitized Douglas fir ovules: 1. megaspore mother cell, 2. meiosis, 3. megaspore, 4. free-nuclear stage, 5. cellularization, 6. central cell differentiation, 7. plant egg maturation and fertilization, 8. megagametophyte storage product accumulation, 9. embryo maturation.