186 Transactions. 



variations in structure which I have found in the prothallus of this same 

 species as it occurs in New Zealand. In a previous paper (16, p. 266) 

 I noted that the length of the shaft varies greatly in the case of different 

 individuals, it being comparatively long in some and in others almost 

 absent, and stated that this arose simply from the fact of the variation in 

 depth at which the spores germinate. With regard to the internal struc- 

 ture of the prothallus, I must anticipate here what I hope to describe more 

 fully in a future paper. The lower primary tubercle not infrequently con- 

 sists of two distinct swellings, and not one only. The extreme basal end of 

 the prothallus constitutes the original tubercle, but the second swelling is 

 separated from this by a slight constriction and occupies a position higher 

 up one side. In some prothalli the development of this second laterallv 

 placed swollen region gives a somewhat lopsided appearance to the prothallus. 

 This will be seen in fig. 21 of the paper cited above (16), and also in fig. 13, 

 which is that of a similar prothallus of L. laterale. In some of the short 

 prothalli the two swellings appear side by side, together forming the basal 

 part of the prothallus, the crown of lobes arising from both together : this, 

 of course, serves to impart a thickset appearance to the prothallus as a 

 whole. Contrary to what botanical writers, quoting from Treub's original 

 papers, have stated with regard to the internal structure of the primary 

 tubercle in L. cernuum, I find that a well-marked differentiation of fungus- 

 inhabited tissues is there to be seen, though, of course, to a much less 

 extent than in the prothalli of the clavatum or coniplanatum, tvpes. The 

 outer peripheral layer of cells is for the most part only one cell in thick- 

 ness, and this contains the spherical coils of fungal hyphae. Those cells 

 of the interior of the tubercle which immediately abut on the peripheral 

 layer are very distinctly elongated at right angles to the latter. They 

 are narrow, and in transverse section are roundish in outline, and in 

 this layer the fungus occupies a position in the cell-walls. In fact, this 

 layer may be compared to the palisade cells in the vegetative part of 

 the clavatum or complanafum prothallus. In some cases I noticed that 

 the cells of this interior tissue contained abundant small bodies which 

 I took to be starch-grains. Apart from those instances in which there is 

 a second swollen fungal region occupying a lateral position, I have not 

 observed the fungus penetrating into the region of the shaft. The two 

 fungal tissues occupy the whole of the first-formed tubercle, but in the case 

 of the second swelling they are, as I have said, laterally placed. If now 

 prothalli of this species occurred in which the fungal regions extended in this 

 way farther up the main body of the prothallus, not only in one localized 

 position but uniformly all around it, leaving a central core of undifferentiated 

 cells, we would have a condition approaching that of the prothallus of 

 L. complanatnm in its basal region, as described by Bruchmann. I have 

 not observed such cases in the prothallus of this species, bu.t what has just 

 been described becomes of some significance in this connection when com- 

 pared with the further variations in the prothallus of L. ramulosum to be 

 described below. In the case of the conrplanatinn and clavatum types of 

 prothallus the main characteristic is that the fungal tissues have become 

 so important a part of the prothallus-body that their development is not left 

 to the mere spreading of the fungus to additional regions of the prothallus, 

 or to the successive infection of those regions from without through the 

 rhizoids, as is obviously the case in L. cernuum. and L. laterale, but proceeds 

 uniformly from the meristem, the vegetative part of the prothallus con- 

 sisting of one large swelling and not several small distinct ones. On 



