啊哈～ 仙人掌

剌座為一高度特化之腋芽或側芽, 或短芽或分枝.
"An areole is a highly specialized axillary or lateral bud or short shoot or branch." ( definition in TCF )
"AREOLE: In xerophytic succulents a localized area of stem with one or more growing points and often spines, bristles, scales or hairs; a reduced spur shoot initially subtended by a foliage leaf or scale leaf." ( Dr. Mauseth, "What is an areole ?" )

仙人掌從一般植物演化成仙人掌也是一樣主要具有三大適應性改變 ( modifications ) 以及四個次要的改變.

主要的三大改變 :

( 這篇是原本貼在仙協中, 屬於比較早的版本, 比較完整的內容請參考 "Part - 0 什麼是仙人掌", 不過有些內容是那篇所沒有的, 所以仍具參考性. )

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怎樣的植物才能稱為是仙人掌 ( Cactus ) 呢 ?