INTRODUCTION. XAl 
measure obviated, I propose to offer a series of observa- 
tions on the respective permanence or disposition to 
vary, of the modifications of each particular organ. 
The habit of Roses, although not often of moment, 
may sometimes be employed with advantage, when its 
differences are caused by the manner in which the 
rootshoots grow. ‘Their being bent like a bow distin- 
guishes Canine and Rubiginose from Villose; in 
which they are quite erect. The flagelliform shoots of 
arvensis prevent its being confounded with systyla; and 
their being climbing separates sempervirens from pro- 
strata. Yet cinnamomea contains two plants, of which 
one has straight and the other curved rootshoots ; and 
the same remark is applicable to tomentosa. 
I have found it necessary to make a distinction 
between branches and branchlets, understanding by the 
latter term the lateral shoots which are produced in the 
same season as those from which they spring. Thus 
R. lutescens is readily known from spinosissima by the 
dense prickles of its branches, and the mere roughness 
of its branchlets. In R. /axva the latter are unarmed ; 
in lucida, furnished with infrastipulary prickles. R. 
rubella is armed as far as its extremities; in the most 
nearly allied species, R. stricta, the branchlets are 
almost naked. R. hystrix has the latter covered all 
over with little rigid setee, while its branches are abso- 
lutely free from them. 
Arms is a term used to express the presence of 
sete and prickles mixed indiscriminately. 
Sete are little straight aculei tipped with a gland. 
They are known from real glands by their rigidity, 
greater length and tendency to pass into prickles. 
They exist at some period I believe in all species upon 
