I have managed to name all the cacti I have from my Encyclopedia so I thought I would share what I have and what they are - you might have the same.
Astrophytum - The globular bodies of plants in this genus are divided by a small numbers of ribs into wide segments, rather like an orange. The cacti are slow growing and become elongated with age.
Astrophytum myriostigma (bishop's cap) - The grey-green body of this cacti is covered with small woolly scales and has no spines. After 4 years, funnel-shaped bright yellow flowers are borne in spring and summer. They are 5cm (2in) across and grow close to the centre of the plant.
Echinocactus - The spherical to shortly columnar plants of this genus have prominent ribs and attractive spines. Their crowns, sparsely covered in wool, bear rings of yellow or pink flowers when the plants are mature.
Ferocactus - Commonly known as barrel cacti, plants in this genus have dramtic, curved spines and rounded shapes.
Ferocactus latispinus (crow's claw) - Straw coloured radial spines surround red central spines, the lowest of which is broad and fiercely hooked. The round or barrel-shaped, grey-green body has prominent ribs. After 10-15 years, white, pink or purple, funnel-shaped flowers 3cm long, appear close to the centre of the crown in spring or autumn.
Mammillaria - Plants of this genus, which is the largest cactus family, are known as pincushion cacti. They are mainly small, often clump-forming and flower reliably, producing small, funnel-shaped blooms. The aeroles are mounted on tubercules.
Opuntia - Plants in this large genus usually have jointed stems, compromising cylindrical or flattened pads. Aeroles are scattered over the stem surfaces and have fine barbed bristles, called glochids. Most species also have spines.
Optunia microdasys (teddy-bear cactus, bunny's ears) - Velvety, pale yellow glochids, which are particularly fine and sharp, grow from the closely spaced aeroles. Mid green pads are 8-15cm long and round to oval in outline. The pale yellow, bowl shaped flowers are produced rarely. They are 4-5cm wide and appear in spring and summer.
I have posted my images of these on the
http://www.flickr.com/photos/23947924@N08/sets/72157604623408425/ - Gardening Photo Album Flickr
