Natural History Wanderings

In a recent article, Rosa macrophylla | Botany Photo of the Day, Botany Photo of the day explains

the difference between prickles, thorns, and spines. Thorns are modified stems, while spines are often modified leaves or stipules. Both of these tend to be quite long and sharp. Prickles however, are outgrowths from the epidermis of the stem tissue; all roses have prickles.