2 
ee pubescentes, Antherae 0° mm. longae, apiculatae. ead 
adm. rudimentarium ; stylus superne minutissime pubesce 
sii capitatum, — Synantherea mexicana, Auct. ex Endlich in einen: 
pfl. vo]. ix. p. 234. 
Nort America. Escondido Creek, south-west borders of Texas, 
Bigelow. Vag AMERICA. exico: on the road from San Luis 
to San Antoni ally 435. Coahuila State: Sierra Madre, Palmer, 
646 ; Parras, Palm , 566; Limestone Hills, Carneros Pass, Pri 
2380; near She Hidalgo, Pringle. Common at altitudes from 
600-2100 m. throughout the Ghikaalie desert, Mexico. 
For a comprehensive account of the Mexican rubber plant here 
figured, the shies oe is referred to Prof. F. E. Lloyd’s book on the subject, 
entitled ‘Guayule, which was published in 1911 by the Carnegie 
Institute of Woktaglon 
he guayule (Parthenium argentatum) was discovered in 1852 near 
Escondido Creek, Texas, by Dr. J. M. Bigelow, of the Mexican Boundary 
Survey. It occurs on the high plateaux from the south-western part 
of Texas throughout the Chihuahuan desert of Mexico as far south as 
Hidalgo. The plant is common on the foot-hills and slopes, especially 
those favoured by a southern aspect and where the soil is highly ca cal- 
careous. According to Lloyd, the country through ey it is distri- 
buted embraces an area of about 130,000 square miles, and he estimates 
that about 10 per cent. of this area carries guayule shrub. 
Before its value as a rubber-yielding plant became known, the shrub 
was used extensively as fuel by Mexican brick-makers, and thus thou- 
sands of acres were depleted. The total original quantity of the plant 
sumption in 1911 the natural supply would be exhausted in six to eight 
years. The rubber already exists as such in the cells of the plant, and 
its extraction cannot therefore be accomplished by bleeding, as in the 
case of latex-bearing plants, but by crushing with machinery and subse- 
quent separation by various methods. The quality of the rubber is 
only moderate. 
Reproduction is carried out by means of suckers and by seeds. The 
manner in which the flower-heads of Parthenium argentatum become 
dismembered is very remarkable. In each head there are two series 
of sees bracts, five in each series, five female ray-flowers, and 
numerous disk-flowers (essentially male) in the middle, each of the last 
ps: enveloped by a sie of the SS When ripe the flowers 
he inner series of bracts fa y from the outer series of bracts, 
which-i is persistent on the peduaie a each ray-flower and ok, or 
the adjacent disk-flowers and their paleae, and their subtendin 
volucral bracts become attached to one another by concrescence a 
