1920 Pease; on Desmarestia 325 



bis plant as a Desmarestia, and then he did so with the comment: "Si 

 c' est un Desmarestia, comme tout le fait eroire, on pent considerer la 

 fronde entiere comme formee par la soudure des pinnules opposees que 

 lepresentent les nervures." 



A few specimens of the proposed new species, D. foliacea, were 

 secured during the summer of 1916, and referred at the time to D. 

 tahacoides Okamura. In the summer of 1918, Avhile collecting over the 

 same ground, an abundance of material was secured in all stages, from 

 plants 2 or S cm. long uij to those about a meter in length. 



In very young plants, the lateral veins can be traced unbranched to 

 the margin of the frond, and a few of these young plants have been col- 

 lected which still show the protruding stubs where the assimilating hairs 

 have broken off. In older specimens, however, the margins are sinuate, 

 with obscure teeth rather widely separated, and the lateral veins which 

 branch out from the midrib do not appear to extend to the edge of the 

 lamina, as in other ligulate species, but break up into a fine branching 

 network. The lateral veins stand almost at right angles with the midrib, 

 and their branches, in turn, are almost at right angles. These secondary 

 branches subdivide again and again, the finer branching being followed 

 easily with a hand lens. This visible network of fine veinlets in the lamina 

 relates the species closely to D. latissima. In fact, except for its extreme 

 thinness, a plant of D. foliacea bears a remarkably close resemblance to a 

 lateral branch of D. latissima. 



The writer has not seen reproducing material. Okamura (1908), in 

 his discussion of D. tahacoides, describes and figures plurilocular sporangia 

 intermingled with sterile hairs, in sori forming irregularly roundish patches 

 on both surfaces of the lamina. To the writer these bear a close resem- 

 blance to a species of Phycocelis which she has found growing on the fronds 

 of several species of Desmarestia (Plate 60, Figs. 1, 2, 3). In the light 

 of work done by Rosenvinge (1891), Kuckuck (1894) and Skottsberg 

 (1907), on reproduction in various species of Desmarestia, it is highly 

 probable that Okamura's interpretation is not correct. 



/. Key to Species 



In accordance with the ideas expressed in the preceding pages, the 

 author wishes to present the following scheme of classification, which 

 affects only the ligulate species of the genus Desmarestia which appear 

 in the Puget Sound region, with the excei:)tion of T>. piniwtinervia INIont. 

 and D. tahacoides Okamura, which are introduced for tlie ))urpose of 

 comparison. 



