1. The ovule of Grindelia squarrosa has one thick integument; the nucellus consists of one layer of cells outside the archesporial cell, which latter functions directly as a macrospore mother cell. 2. The macrospore tetrad consists of a row of four substantially equal cells, of which the chalazal one always gives rise to the embryo sac. 3. After the 8-nucleate stage is reached the sac is divided into six cells, the upper (micropylar) antipodal cell having two nuclei. Cell division between the two antipodal cells and between the micropylar antipodal cell and the primary endosperm cell takes place by means of cell plates on the corresponding spindles. Cell walls are later formed between these cells. 4. The two antipodal cells persist but do not divide. One or both of them grow laterally into the integument, thus forming one or two lateral haustoria, which may extend nearly to the surface of the ovule. 5. Typical double fertilization probably occurs. The fusion of the egg nucleus with one male nucleus was observed. 6. The primary endosperm nucleus divides before the zygote nucleus. Several free endosperm nuclei are formed before cell division occurs within the endosperm. 7. Twelve is the diploid chromosome number.