- C. spinosa has its spines round or awl-shaped, the white flowers, though small, are very numerous in summer.
- The crowns are broad, somewhat awl-shaped, and of nearly equal size.
- The plants present considerable uniformity in general habit, consisting of a short, unbranched stem, bearing the closely-crowded awl-shaped leaves, which in the larger species attain the length of a foot.
- The leaves of this species are awl-shaped, short and rigid, with pointed apex; closely adpressed, they completely cover the branchlets.
- Luteus, 2 ft., has awl-shaped leaves and dense spikes of fragrant yellow flowers; A.