500 BOTANICAL GAZETTE [December 



Fig. 153. — Resting nucleus slightly increased in size. 

 Fig. 154. — Resting nucleus with radiations at one pole. 



Fig. 155. — Section of a mother cell cut obliquely: resting nucleus with 

 radiations at two poles. 



Fig. 156. — Nucleus in very early prophase, situated at one side, with a 

 centrosome-like structure but no radiations. 



Fig. 157. — Nucleus situated at the upper part of the mother cell with 

 two centrosome-like structures and radiations. 



Fig. 158. — Nucleus situated at the upper part with a centrosome-like 

 structure and radiations. 



Fig. 159.— Nucleus situated at the middle part with no radiations. 



PLATE XXXII 



The formation of the zoosporangium of Aglaozonia reptans (continued) 



Fig. 160. — Nucleus of a zoospore mother cell in prophase, chromatin 

 network irregularly traversing the nuclear cavity. 



Figs. 161-168.— Nucleus in synapsis. 



Fig. 161. — Chromatin threads have begun to be arranged in form of loops 

 which become attached by their ends to a part of the nuclear membrane. 



Fig. 162. — Formation of loops is further advanced. 



Fig. 163. — Cross-section of a mother cell; attachment of loops is at the 



side. 



Fig. 164. — Attachment of loops to the nuclear membrane is all the way 

 around. 



Fig. 165. — Some of the loops are quite shortened and thickened, and yet 

 some others are left behind and can be recognized running across the cavity. 



* 



Fig. 166. — Section near the base of crowded loops in contact with the 

 membrane, showing 48 or more isolated cut sections of the loops. 



Fig. 167. — Loops have shortened and thickened. 



Fig. 168. — Nucleus emerging from synapsis: two pairs of chromatin 

 loops are already in the form of chromosomes. 



Fig. 169. — Majority of the two arms of each of these loops are going to 

 form paired arms of bivalent chromosomes. 



Fig. 170. — Diakinesis stage: 24 bivalent chromosomes are present; no 

 polar radiations. 



Fig. 171. — Spindle with two poles has just formed. 

 Fig. 172. — Metaphase. 



Fig. 173. — Polar view of the metaphase, showing 24 bivalent chromosomes 

 at the equatorial plate. 



PLATE XXXIII 



The formation of the zoosporangium of Aglaozonia reptans (continued) 



As the stage advances, gradual increase of the thickening of the cell wall 

 at the tip of the mother cell is noticeable. 

 Fig. 174. — Late metaphase. 

 Fig. 175. — Anaphase: 24 chromosomes at each pole. 



