474 University of California Publications in Botany [Vol. 6 



cylindrical, with acuminate apices ; branches long included in the 

 common sheath; cells 2.5-3.5/* long; heterocysts basal, 2-6 seriate, 

 diminishing in size downward, snbspherical to disk-shaped. 



Growing on rocks interspersed with Rhodochorton Rothii (Turt.) 

 Naeg., in sheltered localities along high-tide level. Cape Flattery, 

 Washington. Type no. 3832, Gardner. 



Of all the known forms of Dichothrix, D. seriata seems most 

 closely related to D. rupicola Collins (1901, p. 290), from which it 

 differs in having longer filaments with greater diameters which are 

 more strict at the apices, in having seriate intercalary heterocysts 

 as well as basal, and in the sheaths not being ocreate. 



Dichothrix minima Setchell et Gardner sp. nov. 



Caespitibus microscopicis, densis, 80-140/a altis ; trichomatibus 

 panels, 2-5, fere in vagina communi inchisis, dilute aerugineis, repe- 

 tite et dichotomo pseudoramosis, e heterocystis superne lente atten- 

 uatis, leviter torulosis, in pilis hyalinis longis abeuntibus ; cellulis 

 basilaribus 4-5/i. diam., quadratis aut paululum longioribus, homo- 

 geneis ; cellulis pilorum, 0.8-1/x diam. ; heterocystis basilaribus, 

 singulis, sphaericis aut subconicis, quam cellulis trichomatis paululum 

 majoribus ; vaginiis strictis, primo hyalinis, mox fuscescentibus et dis- 

 tinctis. 



Filaments forming small, dense clusters 80-140/i high ; trichomes 

 few, 2-5, and almost wholly included within the connnon sheath, pale 

 aeruginous, tapering gradually upward from the heterocyst, slightly 

 torulose, ending in a long hyaline hair ; basal cells 4-5/x diam., quad- 

 rate or slightly longer, homogeneous; hair cells 0.8-1/x diam.; hetero- 

 cysts basal, single, spherical or subconical, slightly larger than the 

 trichomes ; sheath strict, at first hyaline, soon becoming brown and 

 distinct. 



Growing in small tufts on EnteromorpJia sp. along high-tide level 

 and above. Chuckanut Quarry, near Bellingham, Washington. Type 

 no. 544, Gardner. 



The type material of Dichothrix minima was collected in July, 

 1899, and sent to Professor W. A. Setchell. There was a very small 

 quantity and it was placed in the Herbarium of the University of 

 California under no. 100341, awaiting the accumulation of other 

 material. We have not had an opportunity of visiting the locality 

 since and other material has not been reported from elsewhere. It is 

 hoped the appearance of its description here may stimulate further 

 search for it. 



