CONIFERALES (PINACEAE) 285 



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

 (93), Libocedrus (131), and Juniperus (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 disinte- 

 grate, but sometimes the male cell and the tube nucleus divide 

 amitotically, as in Pinus (66, 87). In the case of an archegonial 

 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 Httle cyto- 

 plasm 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 cyto- 

 plasm in the upper part of the egg, and passes to the egg nucleus, 

 increasing somewhat in size. This behavior has been observed in 

 Pinus, Thuja {"j 2), Cryptomeria (g^) , Juniperus (95), and Libocedrus 

 (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 distributed uniformly about the fusion nucleus. 

 The same phenomenon has been observed recently by Nichols 

 (173) in the fertilization of Juniperus communis. 



In fusion the male nucleus presses inward the membrane of the 

 female nucleus (fig. 332), but evidence is accumulating that there is no 

 fusion of the male and female chromosomes, the two chromatic groups 

 being distinct in Lanx (54), Pinus (51,87) (figs. 33 2-33 7), Tsuga(6o), 

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

 Abies (238) the chromosomes are closely approximated, but no rest- 

 ing nucleus is formed. 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 spirems, each of which forms 

 12 chromosomes, 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 prove whether any given chromosome was contributed 

 by the sperm or by the egg. The chromosomes now split longitudi- 

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

 the resting condition. Consequently, there is no fusion of chromatin 



