216 Transactions. 



general form of the prothallus. There is sometimes a single basal tubercle 

 of rounded form (7, figs. 17-20) ; or this basal fungal region may be 

 extended laterally for a distance up one side of the shaft, thus giving to 

 the prothallus a feomewhat lop-sided appearance (7, fig. 21, and figs. 42-44 

 in the present paper). Again, there may be a second fungal region quite 

 unconnected with the first and situated higher up the shaft (figs.' 38, 39, 

 41). Lastly, there may be two distinct fungal regions situated side by 

 side, the two constituting the basal portion of the prothallus and giving 

 it a markedly thickset appearance (fig. 40) I have sectioned several 

 prothalli which showed this latter form. Rhizoids are borne on both 

 fungal swellings in those cases in which two are present. The lobes 

 which are borne at the crown of the prothallus are flattened extensions 

 (7, figs. 17-21), being generally not more than one to three cells thick in- 

 transverse section (figs. 40-42). In one or two instances 1 noticed from my 

 serial sections that there was a group of lobes situated laterally on the shaft, 

 of the prothallus. In fig. 41, this is seen to be associated with the uppermost 

 fungal region, as if the formation of this second fungal zone had initiated 

 a meristematic activity in the adjoining regions of the shaft. The thickest 

 part of the prothallus is always that situated at the base of the crown of 

 lobes. Here is the meristem (figs. 42, 45) from which the lobes have 

 arisen, and by whose continued activity the shaft of the prothallus can be 

 extended in length and its upper region in width. Here, too, the sexual 

 organs are to be found and the young plantlets (figs. 40, 44, 45). I have 

 never found the chlorophyll extending much more than half-way down 

 the shaft. Sometimes the lobes are bright green, or they may show a very 

 slight tinge of colour or be quite colourless, this variation possibly depending 

 simply upon the age of the prothallus. 



L. laterale. — The prothallus of this species corresponds very closely with 

 that of L. cernuum. I have not found that there is such a marked 

 variation in the length of the shaft as is to be found in the latter species, 

 the majority of the prothalli of L. laterale being more of the intermediate 

 length (7, figs. 13-16, and pi. 17, fig. 3). The longest prothallus I have 

 found is that shown in fig. 46. One prothallus of a very large size is 

 shown in fig. 48. It was exceedingly massive in form, and of irregular 

 growth. Its greatest length was in a horizontal direction, and it possessed 

 a crown of irregular short lobes all along the top. It was almost colourless, 

 though perhaps this was the result of its age. It bore a young plant which 

 was of a bright-green colour, the foot of the plant also being bright green 

 and showing very conspicuously through the prothallial tissues. Chamber- 

 lain (3, p. 57) states that in the prothalli of this species examined by him 

 he found no sharply differentiated primary tubercle like that described 

 by Treub in L. cernuum. From his figures it would appear that this was 

 because his prothalli are rather of the short, thickset form. The basal 

 tubercle is always more distinct when the shaft is well developed. I have 

 found that, as in L. cernuum, the basal, fungal region may extend la,terally 

 for a short distance up one side of the shaft, thus giving a lop-sided 

 appearance to the prothallus as a whole (7, fig. 13). Also, as in the other 

 species, there is sometimes a second fungal region higher up the shaft and 

 quite distinct from the basal tubercle (fig. 47). The leafy expansions on 

 the crown of the prothallus of L. laterale are more filamentous and less 

 lobe-like than those of L. cernuum (7, figs. 13-16, and pi. 17, fig. 3, and 

 figs. 46 and 47 in the present paper). This appears also from Chamber- 

 lain's figures. A large proportion of the prothalli examined by me showed 



