Xerophyte

Central Spines

8-10(-12), brown, needle-like, thin, unequal 1-5 cm long. The seedlings have a number of hooked central spines which are lost as the plants mature.

Seeds

The seeds have strongly convex testa-cells.

Description

Coleocephalocereus goebelianusSN|8072]]SN|8072]] is a large growing plant that is quite different from all other species of the genus and has been placed in its own subgenus Simplex by Nigel Taylor. The plants usually forms a solitary unbranched column up to 6 m tall. The flowering areoles are woolly and bristly and fused together to form a distinctive head (cephalium). C. goebelianus has a continuous, lateral cephalium, and in old specimens this lateral mass of wool and bristles can be as wide as the stem and some metres long. The spines are stout, hooked in seedlings, the flowers are white and nocturnal.

Note

goebelianus For Prof. Dr. Karl I. E. Goebel (1855–1932), German botanist and director of the Botanical Garden München.

Cephalium

Up to 1.5 (or more) m long and 20 cm wide, densely woolly, dark, bristly. A lateral cephalium consists of ribs that are devoid of chlorenchyma (green photosynthetic tissue) because all or a vast majority of epidermal cells form trichomes (hairs). Plants can start to grow a cephalium when a metre or so tall. The lateral cephalium continues growing from the apical meristem once the cephalium starts forming, usually without any reversions back to vegetative growth. In cephalia, this intensive trichome production occurs along a continuous segment of a branch, not just at discrete nodes (areoles). In a cephalium, distance between areoles drops to zero (areoles become contiguous), while the size of hairs-rich areoles increases.

Flowers

Bell shaped, white, nocturnal (bat-pollination syndrome), widely spreading, to 5.5 cm long. Pericarpel and flowering tube naked.

Ribs

10-20(-30) with transverse epidermal folds. In both the unbranched and branched specimens, ribs appear utterly vertical until cephalium formation, at which point they appear to bend towards the lateral cephalium.

Stem

Solitary more or less cylindrical and not mucilaginous. Occasionally C. goebelianus has axillary branches arising from lateral cephalia, which is unexpected due to stem asymmetries in cephalia and the resulting mechanical stress. Young vegetative branches usually arise from relatively far down on older well-established cephalia. While the stem tips of these specimens do indeed tilt in one direction, over time, secondary growth seems to compensate for the tilt, allowing these plants to grow to massive proportions, up to 4.5-6 meters tall with cephalia on the top 2.5 meters of such branches. And these are massive cephalia, often enveloping one-third of the circumference of the branch. Determinate growth of areoles on photosynthetic stems would render axillary branching impossible. The only option for axillary branching in C. goebelianus is via the confluent areoles in its cephalium.

Radial Spines

15-20 1 cm or less, white.