Stem without spines
Leaves red/brown/reddish-brown …………………………........Euphorbia cotinifolia
Leaves green or green with variegations
Leaves usually present for short
duration towards the terminal end of stem ..……………......Euphorbia tirucallii
Leaves present for longer duration
not just confined to the terminal ends
Leaves alternate scattered distichously …………............Euphorbia tithymaloides
Leaves alternate, scattered spirally
(not distichously atleast)
Bracts uniformly coloured
(yellow or red or white in colour) …………………….......Euphorbia pulcherrima
Bracts coloured but not completely
Bracts red coloured towards
the basal part ……………………………......………...Euphorbia heterophylla
Bracts white coloured towards
the basal part …………………………………....……...Euphorbia cyathophora
Stem with spines
Stem red/brown/reddish-brown in colour,
normally not more than 1.5cm thick ……………………….......Euphorbia milii
(excluding polyploid hybrids)
Stem green/white/greyish-green/variegated,
normally more than 3cm thick
Stem almost cylindric
Trunk absent, place of attachment
of spines raised ……………………………………..............Euphorbia caducifolia
Trunk present, place of attachment
of spines almost embedded atleast not raised …………...Euphorbia nivulia
Stem angular or winged
Wings 3-4
Wings straight, sinuate or dentate
Stem green without
white bands …………………..............................…Euphorbia antiquorum
Stem variegated with
white or white bands
between two wings …………..…......................…...Euphorbia lactea
Wings spiral ………………………........................…….Euphorbia tortilis
Wings 5-6 ……………………………......................…...….Euphorbia royleana
Varieties may be kept separately I assume.
Key is 98% yours and I just added and deleted few things so even less than 2% of my knowledge involved.
Regards
Pankaj
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"TAXONOMISTS GETTING EXTINCT AND SPECIES DATA DEFICIENT !!"
Pankaj Kumar Ph.D. (Orchidaceae)
Research Associate
Greater Kailash Sacred Landscape Project
Department of Habitat Ecology
Wildlife Institute of India
Post Box # 18
Dehradun - 248001, India