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Transactions. 



a lateral group of lobes borne on the shaft. I previously thought that 

 this was a distinguishing feature between the two species L. cernuum and 

 L. laterale, but have since found it also in the prothalli of the former. In 

 one of the figures given in Part I of this series of papers (7, fig. 16) I showed 

 that a long, thin, club-shaped process is sometimes to be found attached 



to the basal tubercle of the pro- 

 thallus of L. laterale, and I there 

 expressed the opinion that this 

 was the first-formed part of the 

 prothallus, as it so often is also in 

 the prothallus of L. ramulosum. 

 My serial sections of this prothallus 

 unfortunately do not make this 

 satisfactorily clear, but none the 

 less I feel confident that this is 

 the right interpretation. The base 

 of this first -formed process (7, 

 fig. 16) shows the presence of the 

 fungus, and it may be compared 

 with the corresponding parts of 

 L. ramulosum illustrated in the 

 present paper in figs. 52-54. As 

 in L. ^ cernuum, the prothallus of 

 L. laterale is normally short-lived, 

 having decayed away by the time 

 that its plantlet has developed two 

 or three protophylls. Probably 

 the, large size of the prothallus in 

 fig. 48 was due to the fact that for 

 a considerable time no embryo wa 

 formed on it. Moreover, in this 

 case, on account of its large size, the 

 prothallus would persist attached to 

 the young plant for a much longer 

 time than usual. 



L. ramulosum. — The prothalli of 

 this species vary very remarkably, 

 both in form and structure. I 

 have discovered these prothalli in 

 several different localities and in 

 considerable numbers, and so am 

 able to give a fairly complete ac- 

 count of their typical form and of 

 the variations of it. The prothalli, 

 as in the other species belonging 

 to the cernuum type, are more or 

 less green in their upper regions, 

 being situated at the surface of 

 the ground. Some of the prothalli of this species are very similar to those 

 of L. cernuum, while others show on the one hand the elongated arid on 

 the other hand the compact, massive habit which I have described as 

 occurring both in L. cernuum and in L. laterale, but here to a much more 

 marked extent. Figs. 50-55 illustrate prothalli of the elongated form 



Fig. 50. — L. ramulosum. Complete mature 

 prothallus of elongated form in general 

 view, showing several swollen fungal 

 regions, x 30. 



