274 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



2. Cystocarps situated on the midribs of the fertile blades; shoot 

 apex with cross-dividing apical cell ; intercalary divisions absent 

 from the cell rows of the first order ; chief veins in section show- 

 ing descending rhizoids 3 



2. Cystocarps scattered over the fertile parts of the thallus . . 5 



3. Procarps with two carpogenic branches and one group of fertile 



cells ; intercalary cell divisions present in cell rows of the second 

 order; thallus of more than one cell layer Hemineura 



3. Procarps with one carpogenic branch and two groups of sterile 

 cells ; thallus of one cell layer except for the veins .... 4 



4. All tertiary apical cells maintained at the thallus margin ; inter- 

 calary cell divisions absent; midrib present and at least in the 

 oldest parts showing descending rhizoids between the larger cells; 

 lateral veins and veinlets absent Hypoglossum 



4. Not all tertiary apical cells maintained at the thallus margin; 

 intercalary divisions in the cell rows of the second and higher 

 orders present; besides the midrib, microscopic or macroscopic 

 veins present; rhizoids running between the large cells of the 

 midribs Delesseria 



5. Apex of the blade with a cross-dividing apical cell; intercalary 

 divisions present in the cell rows of the first order; no slender 

 rhizoids among the large cells of the midribs 6 



5. Apex of the blade without a prominent cross-dividing apical cell ; 

 intercalary divisions present; principal veins with descending rhi- 

 zoids; branching from the thallus margin 7 



6. Younger parts of the thallus of a single cell layer; midrib present 

 and distinct ; lateral veins opposite, thallus broad, generally pin- 

 nately lobed Phycodrys 



6. Thallus throughout of several cell layers; midrib present, but 

 lateral veins absent ; cell rows of the second order with unequal 

 development on the opposite sides Nienburgia 



7. Microscopic veins absent 8 



7. Microscopic veins present, the procarps with two groups of sterile 

 cells, the carpospores terminal on the gonimoblasts ... 9 



8. Procarps with two groups of sterile cells, the carpospores in 

 chains on the gonimoblasts; monostromatic in the younger parts; 

 veins present or absent, but not dichotomous . . Myriogramme 



8. Procarps with one group of sterile cells ; the carpospores usually 

 single and terminal on the ends of the gonimoblasts, but some- 

 times two together; veins absent Nitophyllum 



