LEEK 



win attain a much larger size; also can be conveniently 

 ii.'tt in tlic trench with slight protection, and taken tliere- 

 ffom for winter use. Care must be taiien not to cover 

 tt>o early, as they decay easily, beginning at the end of 



LEGUMES 



897 



1255. Essential organs of a Sweet Pea flower. 

 Calyx at C; tenth st.imen at A; stigma at E. 



the foliage; this destroys their appearance. The har- 

 dier kinds are used for this purpose and will blanch 

 yellow down to the so-called stem, which is white t*) the 

 root. Leeks planted out in May are ready for use in 

 September; the sowing;? can be made earlier and later 

 to suit the time of maturing, and can be sown in 

 August and September in coldframes and wintered 

 over with slight protection, then transplanted to 

 the open ground in April. The varieties best 

 known to American gardeners are London Flag, 

 Large Musselburgh or Scotch Flag, Giant Caren- 

 tan, and Large Rouen. j_ qtto Thilow. 



LEGUMES. The popular name given to a vast 

 and important family of plants, of which pea, 

 bean, clover, vetch, etc., are common representa- 

 tives. The order is generally known as the pulse 

 family, or Leqnminosa'. It contains nearly 450 

 trenera, comprising over 7,000 species, and in 

 economic importance ranks second only to the grasses 

 {Graminece). The species of this family are distri- 



est trees. Numerous .species are widely cultivated as 

 agricultural crops. Among these, beans and peas are 

 important food-plants, while clover, vetches, peas, meli- 

 lot, alfalfa, lucerne, cow-peas, etc., are valuable forage 

 crops, cover-crops, and green manures. Many of the 

 exotic species are of commercial importance. The ar- 

 boreal forms furnish structural timber and cabinet 

 woods. Many also furnish dye-stuffs, rubber, balsams, 

 oils, etc., and .some are cultivated for ornamental pur- 

 poses. 



In respect to the characterof the flowers, the family is 

 divided into three subfamilies. In the large subdivision 

 to which the ornamental species of Mimosa and Acacia 

 belong, the flowers are small and regular and often 

 clustered in spherical or ol)long heads. The stamens 

 are free or united into a tube and much exerted. In the 

 second subfamily the flowers are usually irregular, with 

 the upper petal folded inside of the others in the bud. 

 The coffee-tree, honey locust, and the large genus Cassia 

 belong in this subdivision. Most of the native species of 



bated over the entire earth. By far the greater number 

 are herbs and half-shrubby plants, but in the warmer 

 regions of the earth thev attain the dimensions of for- 



1257. An indehiscent lesuminous pod— Daubentonia. 



Legumes, and all those cultivated as farm crops, belongto 

 the vast subfamily Papllionarecp, In these the flower is of 

 the papilionaceous type,or pea type (Fig. 1254^. The upper 

 larger petal, called the banner, s, is exterior and folded 

 over the others in the bud. The two lateral ones, situa- 

 ted below the banner, are the wings, iv^ ir, while the 

 lower pair, which are sometimes united, form the keel, k. 

 The keel encloses the stamens and pistil, the latter l)eing 

 often bent at riglit ani^les to the ovary, or coiled. The 

 stamens are either free or they form a tubular sheath 

 surrounding the ovary. Often the upper one alone is 

 free, leaving a slit along the upper side of the sheath 

 (Fig. I'Joo). These tiowers are often dependent on in- 

 sects for pollination, a fact which is of great importance 

 in raising clover seed. 



The fruit of the Leguminosfe is a pod or Legume, as 

 in the bean (Fig. ]2.')()). As a rule, the pods are one- 

 loculed, and have the seeds arranged in rows. In some 

 tribes they become several-celled by partitions which 

 arise between the seeds. These pods become constricted 

 at the partitions, and at maturity separate into short 

 joints (see Fig. 094, Vol. I). The valves of the pods are 

 generally papery or leathery, and open at maturity, often 

 by a sudden snapping of the valves, which scatters the 

 seeds. Inothertribes, however, the pods are indehiscent, 

 or do not split at maturity (Fig. I2o7). 



The roots of Le,2:nmes have numerous small tubercles 

 scattered throughout the root-systems. Fig. 1258. These 

 are caused by and infested with minute organisms, to 

 which the name bacteroids has been applied. The bac- 

 teroids are always present, and probably multiply to 

 some extent in soils where Leerumes have been g-rown. 

 They are very minute bodies, which are either rod-like in 

 forro or branched in the form of a Y or a T. The infec- 

 tion of the plants has been observed to take place 

 through the root-hairs. Within the plant the bacteroids 

 assume a new and peculiar form. They grow out into a 

 branched and flexuous thread, which is enlarged and 

 nodulose at places. At the point of infection the root- 

 cells are stimulated to growth, producing the nodules 

 characteristic of Legumes. The threads permeate the 

 entire tubercle. The old threads finally disorganize, 

 and it is believed that their protein substances are 

 absorbed by the host. 



