366 University of California Publications in Zoology I Vol. 13 



proximally, but very minute distally. In the aftershaft the nodes are 

 ]iot quite so globular, and show rudiments of prongs. In the majority 

 of the Psittaci, the nodes are shaped more like the fruit of a 

 eucalyptus tree, and have the pigment in them instead of proximal 

 to them, thus closely approaching some of the coraciiform birds. 

 The nodes in the Psittaci are somewhat closer together than in the 

 Cuculi, there being usually 15 or more per millimeter, instead of 10 

 or 12 as in the Cuculi. 



d) Color Modifications 



There are a number of interesting color modifications in this 

 order. The steel-blue feathers of Eudynamis honorata have a warm 

 brown pigment, and are highly reflective, the blue color being prob- 

 ably due, at least in part, to the selective transmission and reflec- 

 tion of the pigment. There are raised ridges at the junction of 

 the cells of the bases of both distal and proximal barbules, and also 

 on the broad pennula of the latter. A similar modification is to 

 be found in the glossy green feathers of Geococcyx calif ornianus. 

 In this case the green color seems to be primarily produced by the 

 reflective bases of the distal barbules, but the pennula of the prox- 

 imals are conspicuously broadened, with distinct raised ridges at 

 the junction of the cells (pi. 30, fig. 73a.). 



In the Musophagidae, represented by Turacus corythaix, the 

 barbules of the remiges owe their deep purplish crimson color to 

 an evenly distributed pigment known as turacin, which, according 

 to Church (1893), is somewhat soluble in water and contains a 

 considerable percent of copper. By transmitted light this pigment 

 in thin layers, e. g., in a single barbule, is of a distinct green 

 color, but in thicker layers, as where the flange overlaps the rest 

 of the base, or where two barbules lie on top of each other, it is 

 a deep red. It is, therefore, a fluorescent color, with color proper- 

 ties somewhat similar to those of eosin. The dull glossy green and 

 delicately lined feathers of the back are produced by barbs in 

 which the barbules are evenly pigmented with a brownish color and 

 are green by refraction, while the rami are whitish. 



In the Psittaci a number of interesting color modifications are 

 found. Yellows, reds, and oranges are produced by a pigment 

 evenly distributed in both rami and barbules. Green, blue, and 

 purple are produced by a refraction from the dorsal ridges of the 

 rami, modified by pigmentation in the barbules, e. g., the soft deep 



