| A CHARACTERISTIC SOUTHWESTERN PLANT GROUP. |
By HENRY L. CLARKE.
A CURIOUS fascination gathers round any type of plant life that stands alone, as peculiarly characteristic of some one region of the world; and still greater does the interest become when we find, instead of a single type, an extensive group of closely related types holding a thus isolated position, and constituting a flora of themselves apart from surrounding plant realms. But such instances are rare—their very fewness primarily accounts for the impression they make upon both scientist and general
Fig. 1.—Opuntia, Cereus, and Yuccas.
observer. In one corner or another of every continent botanists have found oddly specialized floras, distinct in aspect and purpose from the general run of vegetable forms. Many of these cases are of insignificant importance, save in their immediate interest to the specialist; some attract greater attention, as filling an especially noticeable gap in the series of plant relationships; a few become of widespread interest not only through unique specialization of structure, but also by virtue of their holding a really
