Luphorbia.] CXX1I, EUPHORBIACE® (BROWN). ‘471 
following descriptions all the measurements are taken from flowers soaked in 
boiling water or preserved in fluid, the diameter of the involucre usually includes 
the glands and their appendages or processes, but not their two horns. Usually the 
involucre-glands are free, but in a few of the terete-stemmed and spiny succulent 
species they are united into one continuous rim-like gland or with only a faint 
indication of lobing; in these there is nothing but habit to separate them technically 
from Synadenium. The formation of a key to the species of this genus presents 
exceptional difficulties, as the characters available are few in proportion to the 
number of species. It is often easy to see at a glance that two or more species are 
perfectly distinct, but very difficult to find absolute characters whereby to distinguish 
them in a key. Leaves are often so similar in a number of species or else so 
dissimilar on the normal stems and those that spring up after the annual fires, that 
distinct species have been founded upon them (as in FB. zambesiaua, EB. depauperata, 
&e.), so that they can seldom be utilised. Pubescence is absent from the majority. 
The involucre and its glands are very much alike in a Jarge number of species, 
whilst in the succulent group the number of angles and spines are very much the 
same in many kinds and the flowers are often unknown, rendering distinctive 
characters exclusive of measurements very hard to find. Among the succulent 
species Pax has proposed groups characterised by the number of spines upon the 
spine-shields, which 1 find to be quite invalid. For the difference in the number of 
spines mentioned by him, depends upon the presence or absence of a pair of 
prickles above the spines. The spines in books have been called “ stipular spines,” 
but as they are always developed below, and sometimes at -a distance below the leaf 
or leaf-scar, they cannot be stipules in the ordinary sense of that term; what their 
real relation to the leaf is I do not quite understand. But the prickles to which I 
above allude are developed one on each side of the rudimentary leaf and are true 
stipules. In some species they seem to be constantly well developed either as small 
auricles or prickles, but with one exception are never so large as the true spines ; in 
other species they are very frequently well developed on some branches and rudi- 
mentary or absent on others or even on the same branch, so that it is often quite 
‘™npossible to use them as specific characters as has been done by Pax, with the 
consequence that the same species is found placed under different names in different 
groups. The term “ flowering-eye ” made use of for the succulent species, refers to 
® more or less distinctly marked and usually depressed area or point, like the “eye” 
of a potato, on the angles of the stem above the spine-pairs, from which the flowers 
ultimately develop. In the following key only characters that are apparently 
absolute have been made use of and where the plant is variable or cannot be dis- 
tinguished by one unvarying character it is inserted under more than one heading. 
A, Plants without spine-shields, prickles or spines, 
With the exception of a few species with rigid 
Woody spine-tipped branches. 
Involucre with only 2-3 perfecterectglands, 
(&-5 or more in allother species); herbs. 
Leaves all petiolate; involucre-glands 3—% lin. long, 
2-lipped, appendaged ; herb with tuberous roots 72. £. tuberifera. 
Leaves sessile at the flowering nodes; involucre- 
glands 1} lin. long, tubular, open down the 
inner side, without appendages ; main stem 
thick, fleshy, tuberculate ; < . 108. E. longetuberculosa. 
Tnvolucre with 4~5 glands, divided on their 
outer margininto 3-15 simple orforked, 
filfform, linear or finger-like processes, 
and including the glands }-1} in. in 
diam, 
