1907] PACE— FERTILIZATION IN CYPRIPEDIUM 



355 



knot, often several of them seem to be attached to the nuclear mem- 

 brane {fig. 6)\ this was seen several times, so that it is probably the 

 usual condition. The synaptic knot is at one side of the nucleus 

 and gradually becomes a compact mass {fig. 7). Even when it is 

 most compact, the constituent threads are apparently distinct, as is 

 suggested in the figure by the rough edges of the knot and by the 

 very evident lines across it. Hundreds of nuclei in this stage were 

 examined and this seems to be the usual condition. 



Upon coming out of synapsis, the threads are no longer in distinct 

 pairs, but in many instances the double nature could be detected 

 for short distances, and occasionally throughout much of the spirem. 

 The threads gradually resume their position near the nuclear mem- 



(fig- 



(fig^ 



ndications 



The chro- 



momeres become less and less distinct, so that with the thick spirem 

 an almost perfect homogeneity seems to exist {fig. p); but even in 

 this stage the double nature of the spirem is often evident, especially 

 when cut ends are examined. There are eleven chromosomes at 

 this reduction division {figs. J2, /j), but it was not possible to 

 determine just how the spHtting takes place — whether transversely 

 or longitudinally. Fig. 10 is at the right stage, but whether these 

 pieces are to be regarded as having about completed the longitudinal 

 sphtting, or as the one long curved and twisted chromosome which 

 will be cut transversely, could not be determined from my material. 

 Pig' ^5 shows a typical spindle for the division of the mother cell. 

 A cell in the wall of the ovule gave the expected count of twenty-two 

 chromosomes for the sporophyte; these were scattered somewhat in 

 the drawing {fig. 14) . 



When first formed, the daughter cells are alike in form and size 

 {fig. 16); but very soon the inner cell shows that it is developing 

 faster than the outer {fig. 17), which also begins to show signs of 

 disintegration. This difference becomes more and more pronounced 

 in the metaphase (Jig. ig) and telophase {fig. 20) of the favored cell. 

 Early indications of the spindle suggest the usual bipolar form 

 {fig. 18), and longitudinal splitting of the chromosomes is shown in 

 fig. 19, so that there is nothing unusual in this division of the daughter 



