Holtz : OBSERVATIONS ON PELVETIA. 35 



sections like Fig. 21 are met with in which it is clearly seen 

 that these lateral basal cells are not the daughter cells of the 

 central basal cell , but that they are the basal cutoffs of the 

 epidermal cells above them. They are, therefore, coordinate 

 with the basal cell a. The cells e and y are later cutoffs which 

 the epidermal cells g and h succeeded in cutting off before be- 

 coming affected by decay. On account of less resistance from 

 the cavity than on other sides these lateral basal cells grow 

 usually in the shape show r n in Fig. 19. 



To summarize my conclusions on this point, the conceptacle 

 originates by a few contiguous epidermal cells cutting off basal 

 cells, Fig. //, which are meristematic, dividing principally 

 periclinally into half a dozen or more tiers of cells. Directly 

 over this meristematic mass of cells, whether by the tension 

 produced by the growth of the cells below, or otherwise, one or 

 several epidermal cells begin to show signs of decomposition. 

 The disintegration proceeds and the cells collapse (Figs, /p and 

 <?/), and a cavity is begun. The disintegration spreads to 

 neighboring epidermal cells and to the cells in the meristem 

 below (Figs. 21, 23 and 25). By their decay the cavity is en- 

 larged. The deeper and marginal cells in the meristematic 

 mass do not disintegrate, but in the end make the inner wall of 

 the conceptacle, and give rise to paraphases and reproductive 

 organs (Figs. 2J, 28, 29). The mucilaginous remains of the 

 decayed cells for a time fill the cavity, or protrude from its 

 mouth, or close the mouth as a stopper. The diagrams, Figs. 

 18, 20, 22, 24., 26, corresponding respectively to Figs. 77, /p, 

 21, 23, 25, illustrate how it is possible to explain the develop- 

 ment of the conceptacle without using Bower's central, persist- 

 ing, basal cell theory. It is not probable that the development 

 of the conceptacle in P. fasligiata is different from that in the 

 closely related plants which he describes. Since this work by 

 Bower is the principal reference we have on the development 

 of the conceptacle in the Fucaceae, and is generally quoted, it 

 would be profitable for others to repeat these investigations. 



Finally the disintegration stops, a healthy surface layer of 

 cells then lines the cavity and the dead and mucilaginous cells 

 are cast off into the cavity. Meanwhile the unaffected epi- 

 dermal cells continue to divide and form their basal cells which 

 pass into the cortex. This new cortical growth stops abruptly 

 at the conceptacle. In this way the cavity is deepened and a 



