Grinnellia americana, Harv. 17 



formed in the neck of the trichogyne. Shortly after this, 

 zoogloea-bacteria collect about the distal end of the trichogyne 

 and cause its rapid disintegration (Fig. 14 b). This shows the 

 evanescent character of the organ, which decomposes and 

 falls away in a short time after receiving the contents of the 

 fusing antherozoid. 



As there is no indication of a conjugating tube connecting 

 the carpogonium to the large auxiliary cell which supports 

 the procarpic branch, and as there are open pores connect- 

 ing the cells of the procarpium, it seems evident that, with 

 the substitution of pores for pits, Bornet's explanation of the 

 method of propagating the fertilizing influence from the car- 

 pogonium to the cell which develops the sporiferous tissue 

 must be accepted in this Alga. 



Very soon after the fertilizing contents of the carpogonium 

 have been transmitted to the auxiliary cell (the large thallus- 

 cell which supports the procarpic branch), it begins an active 

 growth. It increases in size, develops a very thick cellulose 

 cell-wall, and becomes gorged with dense, yellowish, proto- 

 plasmic contents. A similar and accompanying phenomenon 

 is observed to occur in the four large auxiliary cells which 

 immediately surround this supporting cell of the procarp and 

 are found in the plane of the frond (Fig. 16). 



These cells are nucleated, have the same general position 

 with reference to one another (Fig. 25), and form a distinctive 

 group in all young cystocarps. 



In their study of Gracilaria, Bornet and Thuret refer to 

 a group of cells in the basal region of the fruiting body 

 which resemble this group in Grinnellia. In a subsequent 

 investigation of the procarpium and fruit of Gracilaria, 

 Mr. Johnson mentions the same cells and considers them 

 a part of the procarp. In Grinnellia they are auxiliary cells 

 of which the central one develops the sporiferous tissue 

 subsequently to receiving the fertilizing influence of the 

 carpogonium. 



The developmental changes in the young cystocarp are 

 very rapid from this period. The central cell of this group. 



