344 Pub. Fuget Sound Biol. Sta. Vol, 2, No. 53 



4: Summary 



In the taxonomic portion of the paper, the writer has discussed two 

 well established ligulate species of the genus Desmarestia, D. ligulatu 

 (Lightf.) Lamour., and D. lierhacea (Turn.) Lamour. ; has presented a 

 species recently separated from the latter, D. latissima Setch. and Gard. 

 in litt., n. sp. ; and has proposed a new species, D. foliacea n. sp. 



In the discussion of the morphology of these ligulate species, all the 

 available literature has been summarized and the following new points 

 have been presented: 



1. The transitory assimilating hairs during the period of elongation 

 in early spring differ in several species examined, and further examination 

 in other species may lead to the conclusion that difference in assimilating 

 hairs can be made to constitute a species difference. 



2. The primary axis of the assimilating hair is not regularly branched, 

 but branches may occur singly or in pairs, and are separated by a varying 

 rumiber of axial cells. 



3. At the end of the growing season the assimilating hairs are cut 

 off by a definite method of abscission. 



4. The cortical layer does not originate as filaments growing out from 

 the basal cells of branch hairs which become applied to the axial cells, 

 but as two groups of cells cut off from the basal cell of opposite paired 

 branches, which divide without definite order and produce a single layer 

 of cells covering the axial cell and the bases of its lateral branches, and 

 so form a flat thallus. 



5. There are two S3^stems of secondary tissues: (a). The "inner assim- 

 ilation system" and "conducting hyphae" which originate from the cells of 

 the ground tissue. (b). Tlie secondary outgrowths from the lateral 

 branches of the axial filament or "original thallus," which in very broad 

 species form a network of veins in the lamina, visible from the surface. 



6. The cells of the axial filament and all its branches, both j^rimary 

 and secondary, develop into true sieve tubes. 



The writer wishes to express her appreciation to Dr. T. C. Frye, 

 director of the Puget Sound Biological Station, who placed all the facilities 

 of the station at her disposal for collecting and preserving materials, and 

 to Professor Josephine E. Tilden, of the University of Minnesota, who 

 gave invaluable assistance during the progress of the work. 



