146 



appeared in every respect like tlie similar stages in the other 

 species that were studied (Fig. 9). 



In 0. moluccanum none of the prothallia were found to 

 contain more than four cells. These four-celled prothallia usually 

 (Figs. 4 — 8) have the upper cells quite undivided, while the 

 lower had the larger of the two original cells divided by a 

 vertical wall into approximately equal parts. In this condition 

 they remained until all the food material was exhausted. The 

 cells became more and more transparent, and finally died — 

 apparently from starvation. 



In 0. pendulum, however, a number of young prothallia 

 were found which had increased very much in size and under- 

 gone further cell division. The first of these were observed 

 on April 3d and had developed from spores sown in Peradeniya 

 on February 9th; these had been brought to Buitenzorg. These 

 young prothallia (Figs. 12 and 13) had from four to six cells. 

 It was found that in each case the mycorhiza had connected 

 itself with the young prothallium, and evidently had caused 

 the stimulus in its growth. In every case where the young 

 prothallium had more than three cells, there was found an 

 association with the mycorhiza which could l)e easily seen to 

 penetrate into the basal cell. The infection was in all cases 

 due to fragments of mycelium, and in no cases to anything 

 which could be interpreted as spores. The mycorhizal fungus 

 was apparently growing free in the humus where the spores 

 w^ere sown. This soil had been taken from about the roots of 

 the sporophytes which furnished the spores. 



The free surface of the basal cell has its wall decidedly 

 thickened, and it was here that the infection took place in all 

 the specimens seen. The branching mycelium of the mycorhiza 

 was closely applied to the surface of the cell, and a haustoriura 

 was sent down through the cell wall into the basal cell (Figs. 

 13 and 14). This haustorium is pointed at first, but after 

 penetration into the cell its end enlarges and assumes the 

 form of a somewhat thickened worm-shaped body, much 

 thicker than the free mycelium outside. In the cell infected 



