188 MINNESOTA BOTANICAL STUDIES. 



DESCRIPTION OF PLATES. 

 Fig. i. Young plant with group of young branches on the holdfast. 



Fig. 2. Portion of the plant showing the entire edge and form of 

 young fronds (from dried material), x y 2 . 



Fig. 3. An old frond showing lacerated border and perforations 

 (from dried material), x %% 



Fig. 4. A frond showing striations on the lower surface (dried 

 specimen), x^. 



Fig. 5. Plant with fronds almost entirely cut away showing the 

 growing points, the annulations of the stipe and the dichotomous 

 branching, a. annulations. g-p> growing point, f. frond cut off. 



Fig. 6. Small branch showing a rapid succession of laminae, x J^ . 



Fig. 7. Diagram of a tangential cross section of the frond. c. 

 cortical area. int. intermediate. e. bundles of enlarged filaments. 

 /. loosely woven cells of central area. 



Fig. 8. Cross section of a frond showing bundle of elongated cells 

 in central area in transverse section. Letters as above. Drawn with 

 camera lucida. x 250. 



Fig. 9. Cross section of a frond showing a longitudinal section of 

 a part of a bundle of elongated central cells. Drawn with camera 

 lucida. x 250. 



Fig. 10. Cross section of a frond stained for a minute in a strong 

 solution of I in KI. ch. chromatophores. st. starch grains. Drawn 

 with camera lucida. X345- 



Fig. ii. Cross section of a frond through a nemathecium. cent. 

 central layer, p. paraphyses. /. tetraspores. Cells are drawn only 

 in outline. Contents have been omitted. Camera lucida. xS3- 



Fig. 12. Cross section of a frond through a nemathecium showing 

 tetraspores. Drawn from a glycerine mount in which the gelatinous 

 walls became almost entirely obliterated. The walls are, therefore, 

 omitted except around the tetraspores. x 250. 



Fig- 13- Cells from central area showing protoplasmic connec- 

 tions. Camera lucida. x 250. 



Fig. 14. Diagram of cross section of stipe in internode. Letters as 

 in frond. 



Fig. 15. Diagram of longitudinal section of a stipe through a node. 



Fig. 1 6. Diagram of a longitudinal section of the stipe through a 

 growing point. 



Fig. 17. Peripheral cells from cross section of stipe showing the 

 striations in the outer gelatinous covering, x 345. 



Fig. 1 8. Filament from a cross section of the stipe in the cortical 



