CONIFERALES (PINACEAE) 285 



tube, as in Thuja (72), Taxodium (76), Sequoia (92), Cryptomeria 

 (93), Lihocedrus (131), and Jimiperiis (173). The non-functioning 

 male cell and the stalk and tube nuclei, which are carried into the 

 peripheral region of the cytoplasm of the egg, gradually disintegrate 

 there, but sometimes the male cell and the tube nucleus have been 

 observed to divide amitotically, as in Pinus (66, 87). In the case of 

 an archcgonial complex, stalk and tube nuclei disintegrate in the 

 chamber. A peculiar discharge of male cells is described by Lawson 

 (92) for Sequoia sempervirens, the male nuclei invested by very little 

 cytoplasm passing out of the tube and leaving behind the enucleated 

 male cells, which retain their form in the tube. 



In general, the functioning male nucleus slips out of its cytoplasm 

 in the peripheral region of the egg, and passes to the egg nucleus, 

 increasing somewhat in size. This behavior has been observed in 

 Pinus, Thuja (72), Cryptomeria (93), Juniperus (95), and Lihocedrus 

 (131). In Taxodium Coker (76) observed the complete male cell 

 pass to the egg nucleus and infold it, the starch of the male cytoplasm 

 being seen distributed uniformly about the fusion nucleus, and even 

 accompanying it to the base of the egg. The same phenomenon has 

 been observed recently by Nichols (173) in the fertilization of 

 Juniperus communis. 



In fusion, the male nucleus presses inward the limiting membrane 

 of the female nucleus, and the two remain distinct for some time (fig. 

 332). Evidence is accumulating that there is no fusion of the male 

 and female chromatic substance, the two chromatic groups being 

 distinct in Larix (54), Pinus (51, 87) (figs. 332-337)) Tsuga (60), 

 Juniperus (132, 173), and Cunninghamia (180) (figs. 338-340). In 

 Pinus the chromatin is in the resting stage as the pairing nuclei come 

 into contact; but as the sperm nucleus begins to penetrate, both 

 nuclei form distinct spirems, each of which breaks up into 12 chromo- 

 somes, the two groups remaining recognizable until the nuclear plate 

 stage. As the 24 chromosomes become oriented in the nuclear plate, 

 the two groups can no longer be distinguished, and it is impossible 

 to determine whether any given chromosome was contributed by the 

 sperm or by the egg. "The chromosomes now split longitudinally 

 and 24 go to each pole, where the two daughter nuclei pass into the 

 resting condition. Consequently, there is no fusion of cliromatin 



