106 



Transactions. 



nuclei. Apparently the mode of growth is exactly the same as in L. phleg- 

 masia. Both transverse and longitudinal divisions are formed so that the 

 cells at the apex of a branch are equi-dimensional. A short distance 

 behind the apex differentiation of the tissues takes place. Few transverse 

 divisions take place in the central cells, so that elongated cells are formed. 

 Those outside the central cells divide by transverse walls and form ecpii- 

 dimensional cells, which soon become infected with the fungus. Some of 



Fig. 32. — Longitudinal section of vegetative branch of L. Billardieri. a, central cells ; 

 b, fungus-infected cells ; c, single row of cells ; d. peripheral layer : 

 b.c, basal cell of rhizoid ; no, nucleus. X 267. 

 Fig. 33. — Longitudinal section of apex of vegetative branch, a, central cells; b, fungus- 

 infected cells; c, single row of cells; d, peripheral layer; nc. nucleus; 

 i, ii itial ell. X 3(>7. 



the cells of the peripheral layer divide by a periclinal wall (fig. 33, x), and 

 the outer wall of the external cell forms a thick cuticle. The external 

 cell grows out and forms a rhizoid, which may grow out to a great length. 

 The wall which separates the rhizoid from the basal cell is extremely 

 thickened and cuticularized. 



The development of young branches was not followed in detail, but 

 a young stage showed a few projecting cells of the peripheral layer, and 

 below them a few small parenchymatous cells. 



Repeated attempts were made to demonstrate the presence of starch 

 in the cells of the branch, but only the slightest traces of it were found. 



Sexual Organs. 



The sexual branches of L. Billardieri are always dorsiventral, the sexual 

 organs being borne on the upper surface. The presence of sexual organs 

 on any part of the thallus can readily be detected by means of the para- 

 physes which are always present on the reproductive region (fig. 34). The 



