FLORA OP THE GALAPAGOS ISLANDS. 91 



praecipue in parte inferiore phylliculis vestita quae basem versus deorsum 

 ad instar radicorum prolongantur. Sori oosporiferi minuti irregulariter 

 supra frondem sparsi. — Albemarle Isl. : Turtle Pt., March, 1899, 

 Snodgrass & Heller. 



In all the specimens there are leaflets on both surfaces of the fronds 

 except near the tips. They arise from the cortical cells, and have no 

 connection with the fructification which is found on the frond itself. 

 Near the base the leaflets grow downward, become somewhat thicker 

 and twisted and bear on their lower surface the proper rhizoids so that 

 the fronds are attached by what is generally called a fibrous base. In 

 spite of the leaflets which would lead one to refer this alga to the genus 

 Glossophora, it seems to me to be less closely related to G. Kunthii, J. Ag. 

 of Peru, the type of the genus, than to Dictyota crenulata, J. Ag. of the 

 Pacific Coast of Mexico. As originally described from Mexico that 

 species has no leaflets and the base is described as stuposc. In 1884 

 Grunow described a variety from the Canary Islands with leaflets, but its 

 relation to that species is uncertain. The Galapagos species differs so 

 much from D. crenulata as originally described, and from the var. cana- 

 riensis that it must be kept distinct. If material hereafter collected 

 should show that the two species are really forms of a single species, a 

 new description will be needed. The following notes on the microscopic 

 structure of the Galapagos alga will be of interest. 



In the upper part the frond is about 100 fi thick, becoming 200 N u thick 

 below. Above, there is a single medullary layer of large cells 70 ^ x 

 70 fx X 168 fx. and a single layer of colored cortical cells 14^ X 14/xin 

 section. Below, the cortical cells become rather deeper, 22 jx X 14 /x in 

 section, and the medullary cells thicker-walled and comparatively nar- 

 rower, 112 /a X 5Q ft in section, and between the medullary and cortical 

 cells is a single layer of flattened colorless cells, 28 yu, X 28 ix X 90 //.. 

 The tangential walls of the medullary cells are pitted to an extent seldom 

 seen in algae of this order. The oogonia are 80 ll or more in diameter 

 and found in small numbers in scattered sori on the frond. The spines 

 are sharper and more solid than in most of the ciliate species, 24-32 mm. 

 long, the tips deeper colored than the base. 



Padina, Adams. 



P. Durvillaei, Bory, Coquille, 1 47, t. 21, f. 1 (1829). — Albemarle 

 Isl.: Tagus Cove, and Turtle Pt., Feb. & Mar. 1899, Snodgrass & 

 Heller. Chatham Isl. : north, Aug. 1891, Baur as Zonaria lobata. 

 Further distrib. W. Ind., west coast of Am. 



