238 PARASITISM OF CUSCUTA AND OROBANCHE 
In Smilax development proves that the tendrils are nothing 
but the lowermost pinne of a folium tripinatum, the mar- 
gins of the petiole of which, subsequently become dilated, the 
pinnules being outside of the dilatation which originates from 
the margin of base of central leaflet. Perhaps this in one of 
the few instances among Monocotyledones, of a pinnated leaf, 
and an only instance of the origin of tendrils from them. 
Pl. 59. G. 1. Apex of axis of Smilax. 
Same outer leaf removed. 
Same outer leaf removed. 
ame. 
Penultimate leaf and ultimate. 
Ultimate leaf and nascent punctum. 
Same in front. 
Half leaf, lateral inner view shewing that the future 
tendrils are nothing but the continuations of leaves. 
wmm mpm 
n 
PARASITISM OF CUSCUTA AND OROBANCHE AS 
APPLIED TO PHYSIOLOGY. 
During a stay of a few weeks at Cabul in the year 1839, 
I was partly occupied in observations on the parasitism of 
Cuscuta, especially of a gigantic species which literally covers 
many of the Poplar and Singit trees along the watercourses 
of irrigation in that neighbourhood, and I had also oppor- 
tunities of contrasting it with the Parasitism of Orobanche, 
on a species of Cücumis. s 
The species of Cuscuta that occur in Affghanisthan may 
be really said to be omnivorous, and fanciful it may seem, 
they are not the only analogies presented to us between the 
flora and population of that country. 
The disc like suckers not only adhere to every part of the . 
stock, with which they come in contact, being often so numer- 
ous as to appear to coalesce, but they fasten on every other 
plant within their reach, as well as on themselves, forming 
‘Such an intricate and firm union, as to defy every mode of 
separation except with the knife. 
