LEGUMINOSAE 
433 
cosmop. Mimosoideae and Caesalpinioideae are mostly trop., Pa- 
pilionatae mostly temp, (abundant on steppes, &c.). The account here 
given is largely condensed from that of Taubert in Nat. PJl. 
Living in every kind of soil and climate, the L. show great 
variety in habit — trees, shrubs, herbs, water-plants, xerophytes, 
climbers, &c. The roots of most sp. exhibit peculiar tubercles — meta- 
morphosed lateral roots containing the peculiar bacterial organisms 
(Rhizobium sp.) about which there has been so much discussion in 
late years. Plants provided with these are able to take up much more 
atmospheric nitrogen than those not so provided. The plant appears 
actually to consume the ‘bacteroids’ which live in its cells, after they 
have stored up in themselves a considerable amount of nitrogenous 
material. Hence the great value of the L. as a crop on poor soil, or 
as preceding wheat in the rotation of crops; for instead of im- 
poverishing the soil they rather enrich it, either by the nitrogen 
contained in their roots and liberated as these decay, or by that of the 
whole plant if ploughed in as ‘green manure.’ 
The stem is commonly erect, but many climbers occur. Some, 
e.g . Vicia, climb by leaf-tendrils, some, e.g. Bauhinia, by stem-tendrils, 
some by hooks (modified leaves in Caesalpinia, &c., emergences in 
Acacia, &c.), some by twining, and so on. Creeping stems, rooting at 
the nodes, also occur. Thorns, usually modified branches (e.g. Gle- 
ditschia) or stipules (e.g. Acacia), are common. The stems of the 
erect trop. sp. often branch in such a way that the branches run 
parallel and erect, and bear crowns of leaves at the top (p. 155). The 
stems of many lianes are peculiarly shaped, often flat, or corrugated in 
various ways, owing to peculiar methods of growth in thickness. 
The leaves are usually alt., stipulate, and nearly always com- 
pound. Many sp. have very small leaves, e.g. Ulex, or scaly leaves 
and flat stems, e.g. Carmichaelia. The stipules vary much in size 
&c. (see Acacia, Lathyrus, Vicia). The leaves usually perform 
sleep-movements (p. 49) at night; the direction of motion varies, 
some moving upwards, some downwards, or in other ways, but the 
final result is usually to place the leaflet edgewise to the sky. In 
Mimosa and Neptunia the leaves are sensitive to a touch and at once 
assume the sleep-position, recovering after a time. In Desmodium 
gyrans the lateral leaflets execute continuous spontaneous movements 
as long as the temperature is high enough. 
The infl. is apparently always racemose, but with much variety. 
The simple raceme is very common, also the panicle and spike. 
Dorsiventral racemes, resembling the cymes of Boraginaceae, also 
occur (e.g. Dalbergia). The firs, are regular (and then frequently 
polygamous) or irregular (and then usually $ ). The receptacle is 
usually convex or flat, so that at most the flr. is slightly perigynous. 
The calyx developes in ascending order and is usually 5-merous, the 
odd (oldest) sepal being anteiior. The sepals are more or less united. 
