Iloltz : OBSERVATIONS ON PELVETIA. 39 



that Pelvetia odgones divide into eight nuclei and that six of 

 these are afterwards destroyed. Not more than four nuclei 

 could be seen in the material studied. 



The ripe oogone contains two eggs. A delicate transverse 

 partition is laid down across the middle of the oogonial con- 

 tents. Each egg is hemispherical or round-conical in shape. 

 The lower one is often more pointed than the other. Nuclei 

 could not be distinguished with definiteness. 



The oogone increases rapidly in size, swelling to an oval or 

 pear-shaped mass which surrounds itself with a thick gelatinous 

 wall (Figs. 36 and 37). The oogonial wall is at first not differ- 

 ent from that of the basal cell, but it soon thickens and becomes 

 gelatinous so that it swells in water. This thickening continues 

 till in the older oogones the swollen walls present the appear- 

 ance shown in Fig. 37. Stratification is sometimes seen in this 

 wall. 



In dehydrating specimens this gelatinous wall splits into two 

 layers, a thin outer layer, and a thicker, firmer, more densely 

 staining one. These layers often remain in contact at different 

 points and generally at the base where both layers are thin {Fig. 

 36). These two layers are the exochite and meso(endo)chite 

 of Farmer and Williams. 1 From their account it would seem 

 that this double-layered condition is the normal. The obser- 

 vations in this case, however, showed that the division of the 

 oogone wall into two layers was unnatural. For nothing like 

 it was observable in sections mounted in water or glycerine. 

 The splitting is probably due to the tensions set up in the dehy- 

 dration and the thicker mesochite layer is probably formed by 

 the shrinking of the gelatinous middle substance upon the inner 

 layer of the wall, therefore, being denser and appearing- more 

 intensely stained. A similar thing is noticeable everywhere in 

 the dehydrated and stained pith. 



Antheridia. — It is generally possible to find oogonia in any 

 section made through a mature conceptacle. The antheridia 

 are often much scarcer, and search has sometimes to be made 

 through several sections before they are found. There is, how- 

 ever, probably no conceptacle entirely without them. On the 

 other hand, some conceptacles contain a great abundance of 

 antheridia crowded in bunches among the oogones and para- 



1 Contribution to Our Knowledge of the Fucaceae : Life History and Cy- 

 tology. 



