Final answer:
Most cacti have reticulate venation, forming a net-like pattern on the leaves. Ginkgo biloba exhibits dichotomous venation. Some cacti have modified leaves, like spines.
Step-by-step explanation:
The leaf venation, or vein pattern, of a cactus can vary depending on the species. However, most cacti have reticulate venation, which means the veins of the leaf form a net-like pattern. This can be seen in dicot leaves, where the veins branch out and create a complex network across the leaf surface.
For example, the Ginkgo biloba tree, which is not a cactus but has a similar leaf structure, exhibits dichotomous venation. In this pattern, the veins fork and divide, creating a dichotomy or branching pattern.
It's important to note that not all cacti have leaves. Some species have evolved to have modified leaves, such as spines, for water storage and protection against herbivores.