147 



with the fungus, the contents show the peculiar aggregated 

 appearance characteristic of the infected cells of the older 

 prothallium. On April 6th a specimen with seven cells was 

 found (Figs. 15 and 16). Observations on the further develop- 

 ment of the prothallia were interrupted by a trip to Tjibodas, 

 which lasted over a month. The cultures were left at Buiten- 

 zorg, and on my return in May observations were resumed. 

 On May 24th several yoing prothallia were found, and on May 

 26th a number more. The largest of these had, as nearly as 

 could be determined, thirteen cells. This was the largest 

 number found in any of the 3'oung prothallia (Figs. 18 — 20). 



These largest prothallia show that as in 0. moluccanum, the 

 divisions are mainly in the lower cell so that the apex of 

 prothallium probably as in the true ferns develops in the lower 

 of the two prothallial cells. The upper cell, however, also 

 undergoes further divisions, and there is no very marked 

 difference between the upper and lower 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 cernaum (Treub — Etude; sur les Lycopodiacees, 

 Annales du Jardin Botanique de Buitenzorg IV, PI. IX, Figs. 

 4—8). The mycorhiza penetrates the adjacent upper cells and 

 in the cells so infected the contents quickly assume the 

 characteristic aggregated appearance, while the apical 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 

 the normal succession of cell division, 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 early divisions. Fig. 20 shows the 

 surface view of one of the largest specimens, with probably 

 thirteen cells. Fig. 19 shows three optical transverse sections 

 of the same. In these larger prothallia there is already the 

 beginning of the axial tissue. Whether the cell x (Fig. 19) is 



