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1903] FLORA OF SOUTHERN CALIFORNIA 271 
clusion. This may be said to be the rule with desert shrubs, and 
it also prevails to a considerable degree in the Cismontane area. 
The storage of supplies at times when they are attainable, so 
that vitality may be preserved through a season when they can- 
not be secured, is provided for by a thickening of either the 
stems or the leaves. 
The engorgement of the underground stem or its buds, 
whereby bulbs and tubers are produced, is comparatively rare 
among the plants of our region. Among the xerophilous plants 
of the Desert there are but two bulbs, Hesperocallis occidentalis 
and Calochortus Kennedyi; and there are two species of Psoralea 
and three or four cucurbits which have tuberous roots. A few 
plants, like the lomatiums, have thickened roots. In the Cismon- 
tane area the list of plants of this kind is longer, but not greatly. 
The Cactaceae are our only examples of the modification of 
the above ground stem for storage purposes. During the wet 
Season these stems become plump and full of sap, but at the 
conclusion of the dry season, they are shrunken and corrugated. 
This is especially noticeable in the opuntias, but it may be 
observed also in the appearance of the ribs or the mamillae of 
the other genera at the different seasons. 
Storage in the leaves is exemplified by the agaves, the cotyle- 
dons, and the sedums. The leaves of these plants also become 
more or less shrunken by the end of the dry season. 
But much commoner than these modifications are the protec- 
tive devices by which transpiration is limited. Few are the 
plants of the deserts which have not acquired one or more 
adaptations whereby this result is effected. Some, like canotia, 
the ephedras, the cereuses, and the echinocactuses, are entirely 
leafless; others, like the opuntias, Dalea spinosa, and Hoffman- 
Seggia microphylla, have the leaves few, small, and early deciduous. 
_In plants such as these, the modified epidermis is chlorophyllous 
and performs the office of leaves. In place of the broad thin 
leaves displayed by the plants of moist climates, these denizens 
of the deserts have small and thick leaves, often with revolute 
edges and pinnate divisions. Very commonly the foliage or the 
whole plant is protected by a coat of hairs, wool, or scales, a var- 
