16 MINNESOTA BOTANICAL STUDIES. 



kinds of medullar)' filaments, and says further, in describing 

 the smaller filaments : " In partibus adhuc junioribus frondis 

 sunt haec fila tenuiora longitudinalia, a quibus fila strati corti- 

 calis exeuntia observare, credidi." Specimens of a species of 

 Liagora belonging to this subgenus, and probably Liagora 

 lefirosa (Tilden, Josephine E., American Algee, Century V., 

 417), have been examined in connection with the preparation of 

 the present article, and in them the origin of the smaller medul- 

 lary filaments was found to be identical with that in Trichog- 

 Icea lubrica. It is easy to see how the mutual relationship of 

 the cortical and the smaller medullary filaments might be mis- 

 understood, and it is suggested that further observations may 

 show the smaller medullary filaments to be of cortical origin in 

 the other species of Liagora, also. 



Cytology of the vegetative tract. — In material stained with 

 acid fuchsin, or with anilin-water-safranin the nuclei appear as 

 nearly spherical densely staining bodies. With the exception 

 of the cells of the larger medullary filaments, in which no satis- 

 factory nuclear stains were obtained, each cell contains a single 

 centrally located nucleus. The nuclei of the outer cortical 

 cells are 2-5 mic. in diameter, those of the other parts of 

 the frond generally somewhat smaller. None of the material 

 was preserved with intention to show division stages of the 

 nuclei. 



Surrounding the nucleus and lying close to the outside of the 

 cell is the chromatophore. This body is irregularly ring-shaped, 

 with processes running inward towards the nucleus. In the 

 spherical cells of the outer cortex the chromatophore almost fills 

 the cell, but in the more elongated cells of the inner cortex, it 

 forms a comparatively narrow band about the center of each 

 cell. As it stains heavily with acid fuchsin, it often entirely 

 conceals the nucleus, so that, especially in the outer cortex, the 

 nuclei can be studied to advantage only in sectional material. 

 In the vicinity of the chromatophore there is often a deposit of 

 floridean starch. This is most abundant in the special photo- 

 synthetic cells, but is found also in other cells which contain a 

 chromatophore. The cells of the smaller medullary filaments 

 resemble those of the cortical filaments except in shape. They 

 have a very narrow chromatophore. The cells of the large 

 medullary filaments have no chromatophore and no distinctly 

 staining nucleus was seen in them. 



