THE GAMETOPHYTE 



attempts to carry them beyond this stage failed and after exhausting the spore con- 

 tents they soon died. The small amount of chlorophyll occasionally found in these 

 young prothallia is evidently insufficient for their independent growth, and after a 

 few weeks the granular contents all disappear and the cells soon collapse, showing 

 that the young gametophyte has died from starvation. 



A number of specimens of the rare Ophioglossum intermedium were collected 

 near Buitenzorg and a few ripe spores were also secured. These spores contain 

 somewhat less dense contents than those of the other species described and have a 

 more delicate epispore. Spores were sown on March 30 in Buitenzorg, and when 

 examined about two weeks later no germinations were found, nor did a second 

 examination about the end of April show any further results. On May 21, however, 

 two three-celled prothallia were found, and subsequently a small number of others, 

 but no later stages were discovered. The young prothallia appeared in every 

 respect like the similar stages in the other species (plate i, fig. 6). 



In Ophioglossum pendulum a number of young prothallia were found which 

 had increased very much in size and undergone further division. The first of 

 these were observed on April 3, and had developed from spores sown in Peradeniya 

 on February 9. These young prothallia (fig. i, c) had from four to six cells. It 

 was found that in each case the mycorrhiza had connected itself with the young 

 prothallium, and evidently had caused a stimulus in its growth. In every case 

 where the young prothallium had more than three cells there was found associated 

 with it the mycorrhiza, which could be easily seen to penetrate into the basal cell. 

 The infection was in all cases due to fragments of mycelium, and in no case to any- 

 thing which could be interpreted as spores. The fungus was apparently growing 

 free in the humus where the spores were sown. This soil, as we shall see, was 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 mycorrhiza was closely applied to the surface of the cell and a haustorium was 

 sent down through the cell wall into the basal cell (fig. i, m). This haustorium is 

 pointed at first, but after it penetrates into the cell it enlarges and assumes the form 

 of a somewhat thickened worm-shaped body, much thicker than the free mycelium 

 outside. In the cell infected with the fungus, the contents show the peculiar aggre- 

 gated appearance characteristic of the infected cells of the older prothallia. On 

 the 6th of April a specimen with seven cells was found. About a month later, a 

 number of other specimens were observed also, some of these having as many as 

 thirteen cells (plate i, fig. 9). This was the largest number found in any of the 

 young prothallia. 



The divisions of these young prothallia are mainly in the lower cells, so that 

 the apex, as in the prothallium of the true ferns, develops mainly from the lower of 

 the two original prothallial cells. The basal cell, however, also undergoes divisions, 

 and there is no very marked difference between the lower and upper ends of the 

 prothallium. At this stage there is a marked resemblance, except for the absence 

 of chlorophyll, to the early germination stages of Lycopodium cernuum (Treub 1). 

 The mycorrhiza penetrates the cells adjacent to the one first infected, but leaves the 

 apical region free, and this region probably remains permanently free from the 

 endophyte, as it does in the adult prothallium. 



The number of young prothallia found was too small to make it possible to 

 determine exactly what may be considered to be the normal succession of cell divi- 

 sion and whether at this early stage there is a definite apical cell could not be decided. 

 As will be seen from the figures, there is evidently a good deal of variation in the 



