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Transactions. 



is sometimes a second fmigal region quite distinct from tlie first, which 

 may be situated either higher up the shaft or at the base alongside the 

 primary tubercle. The characteristic difierence in structure between the 

 basal tubercle and an upper fungal area is clearly shown in fig. 39. The 

 details in the basal structure of the other form are illustrated in fig. 40, 

 the right-hand tubercle here being cut not quite medianly. 



The shaft is built up of large cells whose long axes are directed towards 

 the growing apex. In some prothalli this shaft is long and thin (figs. 38, 42), 

 but in others it is short and thick (figs. 40, 44). An instance in which a 

 lateral group of lobes is borne on the shaft is given in fig. 41, these lobes 



Figs. 66, 67. — L. cermmm. Transverse sections of the basal tubercle of prothallus, 



showing distribution of fungus. X 42. 

 Fig. 68.^ — L. cernuum. Longitudinal section of portion of fungal area shown in fig. 41. 



X 135. 

 Fig. 69. — L. ramulosum. Me'dian longitudinal section of basal tubercle of massive 



prothallus shown in Plate XV. X 42. 

 Fig. 70. — L. ramulosum. a and b, longitudinal section of an elongated prothallus 



with three fungal regions, the basai tubercle being shown at b. x 48. 



c, longitudinal section of apical head of the prothallus shown in fig. 70a. 



X 75. 

 Fig. 71. — L. ramulosum. Longitudinal section of two adjoining fungal regions in a 



large elongated prothallus. X 42. 



here being in conjunction with a second fungal zone. At the top of the 

 shaft is the crown of lobes, these being in transverse section from two to 

 four cells in thickness (figs. 40-42, 44). In amongst the bases of these 

 lobes are situated the sexual organs (figs. 40, 44). Some of the prothalli 

 bear organs of one kind only, that shown in fig. 40 bearing numerous 

 antheridia but no archegonia. Others, again, bear both, as in the case of 

 the massive prothallus shown in fig. 44. 



L. laterale. — The structure of this prothallus corresponds more or less 

 closely with that of L. cernuum. In the fungal regions, whether at the base 

 of the prothallus or higher up the shaft, the hyphal coils are confined to 

 the epidermal cells, and the hyphae penetrate the adjoining tissues in an 



