象牙丸屬多肉植物，原產墨西哥。莖扁球形到圓柱形，直徑最大8~15cm，高6~12cm，外皮橄欖綠色，球先端凹陷，生長點覆有絨毛。5~8道疣狀突起螺旋排列，疣末端有刺座；中刺1或3支，長約1cm；側刺10~20支。花開於球頂，漏斗形黃色花，直徑5~7cm。

A succulent plant, native to Mexico. The stem is shaped flat globose to cylindrical, with a diameter of 8~15cm and a height of 6~12cm. The outer skin is olive green with concavity on the apex, and the growth point is covered with villi. Five to eight ball-shaped verrucae arranged spirally with areoles borne at the end of protrusions; 1 or 3 central spines about 1cm long; 10~20 radial spines. It bears yellow funnel–shaped flowers on the top of the globe, with a diameter of 5~7cm.

栽培：全日照通風環境下可生長良好，日照充足時可促進開花，炎夏時切勿讓植株曝曬，以免產生日燒等曬傷跡象，為了防止爛根等情形，種植時需採用排水透氣的介質。此外，冬季溫度不可低於攝氏15℃。於冬季時植株進入冬眠期，生長緩慢，可移至室內明亮處，控制澆水，若低於攝氏10℃以下，會使其凍傷，影響生長。

The plant enjoys full-sun and ventilated environments. Sufficient sun exposure can promote flowering but direct exposure in hot summer will cause marks of sunburn. Plant in well-drained and breathable medium soil to prevent roots from rotting. The plant will go dormant if the temperature is lower than 15 °C, move it to a bright indoor location and control watering. If the environment is below 10 °C, it will cause frostbite and affect the growth.

多肉植物因其型態特殊，常被應用在植物推廣教育，進行觀賞品種育種選拔，甚至在特殊景觀佈置、花藝組合盆栽，居家綠美化種植上擁有不可或缺的地位。

Because of its unique shape, it is often chosen to present in plant promotion programs which carry out ornamental breeding competitions as well as in special landscape layout and floral combination potted plants. It has an indispensable role to home greening and landscaping.