118 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 26 



PLATE 6 



Fig. 1. Antithamnion kylinii Gard. Mid-part of a sterile plant showing an 

 indeterminate branch with determinate branch opposite, adaxial se- 

 cund branching of determinate laterals, and gland cells, X 55. 



Fig. 2. Antithamnion pygmaeurn Gard. Habit of a sterile plant showing in- 

 determinate branches lacking opposite determinate branches, X 55. 



Fig. 3. Antithamnion hubbsii sp. nov. Part of a sterile axis of the type 

 collection, X 42. 



Fig. 4. Antithamnion plumulum (Ellis) Thuret. Part of a tetrasporangial 

 plant showing tendency toward Platythamnion pectinatum. X 40 

 (after Feldmann-Mazoyer). 



