THE PHANEROGAMS OF THE JUAN FERNANDEZ ISLANDS 191 



of this section R. gracilis differs from the others by its small, narrow leaves 

 and less constricted involucre with obsolete calyculus. Habitually, it is equally 

 distant from all the other species. 



Key to the genus Robinsonia. 



I. Pappus of $ flower forming a tube, including the persistent corolla. Leaves 

 with a very dense net of small pellucid venules between the nerves. 



Subg. I. Symphyochaeta (DC.) Skottsb. R. macrocepkala Dene. 

 II. Pappus bristles free, caducous as also the corolla. Leaves with a much 



coarser net of veins Subg. II. Eleutherochaeta (DC.) Skottsb. 



A. Involucral scales soldered. Leaves distinctly acuminate. 



Sect. 1. Symphyolepis Skottsb. 



1. Scales cohaerent almost to their tips. Inflorescence rounded— flat. 

 Leaves c. 12 cm long, with numerous lateral veins almost parallel 

 with the midrib _ R. Guyana Dene. 



2. Scales cohaerent to Vs. Inflorescence pyramidal. Leaves c. 20 cm 

 long with lateral veins forming a conspicuous net with large meshes. 



R. thurifera Dene. 

 R. Scales free. Leaves acute, but not distinctly acuminate. 



Sect. 2. Eleutherolepis DC. 



1. Calyculus conspicuous. Leaves 8—15 cm long. 



a. Leaves fleshy with thick base, leaving semilunar, flat scars. 



R. evenia Phil. 



b. Leaves coriaceous with less thickened base, leaving linear, 

 prominent scars R. Masafuerae Skottsb. 



2. Calyculus indistinct. Leaves about 3 cm long. R. gracilis Dene. 



125. R. macrocephala Dene. — Johow, Estud. 57. — Fig. 33 a— c. 



Masatierra: Pto Frances, Loma Incienso (called thus after the Robin- 

 sonia), c. 360' m, scattered, specimens (past fl.-fr. 13 /ia 16, no. 131, also observed 

 by JOHOW); hills between Pto Frances and Rabanal (Johow); Co Centinela, 

 steep slope near the entrance to El Pangal, some few shrubs c. 300 m (fr. 28 /3 17, 

 no. 573). 



The pappus of this species is quite unique, forming a closed, tough and 

 firm tube with a wrinkled surface. The achenes, glabrous in other species, are 

 setose in this. The calyculus consists of few, minute bracts. The involucre 

 in the $ measures 10 — 12 mm in length by 8 — 9 across; the head is about 

 15 mm long and 10 mm broad. The scales number 17 or 18 and are firmly 

 soldered. The ray florets are 5 to 8, but sometimes only 2 or 3, sometimes 

 none at all, according to Johow. They are about 10 mm long; the ligule is 

 atropurpureous, boat-shaped, 2 X 1 mm, not smaller than in other species in 

 contrary to older statements. The disc florets are yellow with reddish lobes, 

 8 — 8,5 mm long including the ovary. When the fruit is ripe, the involucre 

 bursts open in a quite irregular fashion. The achenes are much larger than in 

 other species, 7 — 8 mm. 



