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Transactions. 



is a transverse section of the prothallus shown in fig. 5 at aa, and represents 

 the most forward position occupied by the fungus in this prothallus. It 

 will be seen that the fungus in the lateral branch which is also included 

 in this figure is not in connection with that in the main body. The same 

 figure would also represent in transverse section the appearance of the 

 prothallus shown in fig. 2 at cc. 



The generative portion of the central prothallial body is always the most 

 bulky, and shows no di&rentiation of its tissues whatever. Immediately 

 behind the growing apex of the prothalli shown in figs. 2, 3, and ■ 5 

 yoimg antheridia are being produced. Fig. 16 represents a transverse 



Fig. 17. — L. Billardieri. Transverse section of the prothallus shown in fig. 3 at the 



point b. X 135. 

 Fig. 18. — L. Billardieri. Transverse section of the dorsal side of the prothallus shown 



in fig. 2 at the point b. X 135. 

 Fig. 19. — L. Billardieri. Oblique section through the prothallus shown in fig. 2 at 



the point a. X 135. 



suction of the prothallus shown in fig. 3 at a. Fig. 17 is a transverse 

 section through an older antheridial zone of the same prothallus at h, while 

 fig. 18 shows the grouping of the archegonia in amongst the paraphyses 

 on the prothallus illustrated in fig. 2 at hb. The sexual organs occur in 

 large numbers in distinct zones. The close grouping of the antheridia, 

 for example, is shown in fig. 19, which is an oblique section taken through 

 the point of the prothallus illustrated in fig. 2 at aa. The generative region 

 in transverse section bears evidence of repeated cell-divisions, and the cell 

 nuclei and contents are very prominent, as if there had been extensive 

 translocation of food material to this region of the prothallus. A longitudinal 

 section of the generative region shows that the extensive development of 

 sexual organs and paraphyses along the dorsal surface brings it about that 



