214 



BOTANY 



B 



A 



D 



Fig. 77. — Microsporogenesis in Lathrcea (A) L. clan- 

 destina. Presynizetic nucleus with chromatic 

 aggregations held in meshes of reticulum. 

 (B) Synizetic knot. (C) Loosening of synizetic 

 knot. (D) Further loosening of knot. Thickened 

 portions of thread can be seen in contact with 

 nucleolus. (E) L. sqiiainaria. Formation of 

 chromosomes on reticulum. (After Gates and 

 Latter, J. Roy. Micr. Soc.) 



When contrac- 

 tion of the reticu- 

 lum has reached 

 i t s maximum 

 the synizetic 

 knot is extreme- 

 ly condensed 

 (Fig. 77. B), 

 and large masses 

 of densely-stain- 

 ing homogeneous 

 material are pre- 

 sent in the knot. 

 At the initiation 

 of the late 

 synaptic stages, 

 the change from 

 the granular 

 appearance of 

 the reticulum to 

 that of a well- 

 defined thread 

 is very marked 

 (Fig. 77, C). As 

 the knot loosens 

 out, it can be 

 clearly seen that 

 the chromatin is 

 unevenly distri- 

 buted along the 

 thread, and also 

 that the latter 

 remains in con- 

 stant association 



with the nucleolus. When every trace of the synizetic knot has 

 disappeared, the branched loops of the thread lie on one side of 

 the nucleolus, apparently radiating out from it (Fig. 77, D). Those 



