70 MINNESOTA BOTANICAL STUDIES. 



Strbmfelt, H. F. G. Untersuchungen iiber die Ilaftorgane der Algen. 

 Bot. Centralbl. 33: 3S1. 18SS. 



Explanation to Plate XV. 



Figure 1. Form of typical thallus, two fifths natural size. 



2. Irregular form of older thallus caused by rupturing of membrane, 

 two fifths natural size. 



3. Thallus showing irregularity of upper surface cells, two fifths 

 natural size. 



4. Cross section of thallus showing closely appressed outer cells and 

 increasing separation of inner cells, x 16S. 



5. Cross section showing interior needles of cell, x 45. 



6. Cross section showing early development of needle, x 4SS. 



7. Origin of needles, X 4SS. 



8. Basal dichotomous branching of needle, x 4SS. 



9. Apical dichotomous branching of needle, x 4SS. 



10. Origin of haptera ; development of two main branches ; surface 

 extension of lobes and cross beams, x 212. 



11. Diagram of intercellular space showing oval rings representing 

 main branches ; wide and narrow expansion of lobes; branching in 

 various directions and at different levels : stalks or main branches of 

 various lengths. 



12. Cross section of three main branches, ventral and hollow stalks, 

 X 464. ■> 



13. Youngest development of stalk of haptere, x 424. 



14. Concave center of haptere from ventral view, x 360. 



15. Rhizoid on ventral surface with haptere, x 45. 



16. Youngest development of foot on ventral surface, x 45. 



17. Peripheral protoplasmic layer of chromatophores, X 35. 



18. Widely separated chromatophores of inner cell, X 318. 



19. Early development of pyrenoid with central grain and forma- 

 tion of first starch grains, X 760. 



20. Older stage of pyrenoid; scattered starch grains and central 

 grain, x 760. 



