Female Gametophyte of Microcycas

Abstract

1. The ovules were not young enough to show the megaspore mother cell or the megaspores, the youngest stage of the female gametophyte showing free nuclear condition in the megaspore. 2. In older ovules, nuclear division has increased the number of free nuclei, while at the periphery some of the nuclei are already enclosed by walls. Still older ovules show the gametophyte to be completely cellular. 3. The number of chromosomes is twelve, although occasional nuclei have fourteen. 4. The megaspore membrane increases in thickness from 1.5 μ in August to 3 μ in October, and thereafter decreases to 1.0 μ in March. 5. The cells of the nucellus adjacent to the gametophyte are early organized into a nutritive jacket, which persists until the middle of December. 6. The vascular bundles belonging to the inner fleshy layer of the ovule divide and give rise to branches which enter the nucellus. 7. The archegonial initials are distinguishable about the latter part of November. They are scattered in groups over the surf...