PLATE XXL— LEGUMINOS.ffi— SWEET PEA (Lathyms odorata), principally. 



This large and important Order is only known to us in Britain as having irregular butterfly-shaped flowers, but in tropical regions 

 the flower assumes a more or less regular form. The Order is thus capable of division into sections: — i. Mimoseae — represented by 

 Acacia, or Mimosa — the Sensitive Plant, having regular flowers ; 2. Caesalpinieaa — represented by Cassia — having irregular flowers but not 

 butterflied ; and 3. Papilionaceae — our British representatives — having flowers of the well-known Pea type, with a corolla fancifully 

 resembling a butterfly, hence called papilionaceous. 



The action of insects alighting on the Pea flower, for instance, may be imitated by pressing down the wings, and the keel goes 

 along with them, thereby exposing the anthers and stigma. 



M mose^e. — Flower, regular. Petals, valvate. Stamens, definite or indefinite. 



Fig. 1. and Diagram I. — Calyx of five united Sepals. 



Corolla of five Petals. 

 Androecium of numerous free Stamens. 

 Gyncecium of one Carpel. 



C^esalpiniEjE. — Flower, irregular. Petals, imbricate. Stamens, definite. 



Fig". 2. and Diagram II. — Calyx of five free Sepals. 



Corolla of five free Petals. 

 Androecium of ten or less free Stamens. 

 Gyncecium of one CarpeL 



Papilionaceae — Flower, irregular. Petals, imbricate. 



Fig. 3. Compound leaf with Stipules which arise from the base of leaf-stalk rnd not from stem. 



There are two ordinary leaflets, then the next pair are modified into coiled tendrils, and the end of the leaf- 

 stalk is prolonged into branching tendrils. 



Here the leaf or part of it is modified into an organ of support, enabling the weak stem to ascend. 



Fig. 4. The Pea flower in its natural position, presents its standard to the breeze, so that it may act as a fluttering flag to attract 

 insects, and as a shelter to the more delicate inner parts. But when an insect alights on the Wings which are of 

 the nature of a platform, the win<j;s and keel are depressed, and the anthers and stigma are exposed, but return 

 again to their old position when the pressure is removed. The insect, while searching for pollen or nectar in the 

 staminal tube, will undoubtedly carry away some pollen amongst its hairs and leave it on visiting other flowers. 



Fig. 5. Cut the flower in two from the base upwards. 



Sepals, united about half-way down and inserted on receptacle. 



Petals — Standard is towards the main floral axis and therefore dorsal in position. 



Wings, one on each side, therefore lateral in position. 



Keel, of two partially united petals, is away from the main floral axis and therefore ventral in position. 



Stamens, one free, rest united into a tube. 



Carpel in the middle, arising from receptacle. 



Diagram III. — Calyx of five united Sepals. 



Corolla of five Petals. Dorsal petal or Standard overlaps the rest in bud. 

 Androecium of ten Stamens — dorsal stamen free, other nine united. 

 Gyncecium of one Carpel, and the Ovules are out-growths from its margins. 



Fig. 6. Petals of unequal size and shape. 



(a.) Standard laterally expanded, and tightly clasping rest of flower at base. 



(&.) Wing with interlocking processes at base for keel. 



(c.) Keel in natural position enclosing Stamens and Carpel, and forming a tight fit with keel 



Fig. 7. Stamens. 



Filaments united for the greater part of their length into a Staminal tube. 

 Dorsal filament free to about base. 



Fig. 8. Fruit — a Pod or Legume, from which the Order derives its name. 



The Calyx still persists, also the slender Style and even the withered Stamens. 



Figs. 9 and 10. Steep some peas for a night in water, when they may be conveniently examined. 



On the outer surface of Sweet Pea observe elongated scar in the centre indicating its point of attachment 

 inside the fruit, a small opening below, through which moisture can be squeezed, indicating the micropyle. 



In section of Garden Pea observe that when the skin is removed nothing is left but the Embryo consisting of 

 Stem-bud or Plumule. 



Primary root or Radicle pointing towards micropyle. 

 Seed-leaves or Cotyledons. 



Fig. 11. Germination. 



The Radicle has elongated, producing the primary root or Tap-root, with its Rootlets. 



The Plumule also grows upwards, producing at first the insignificant small leaves gradually growing larger as 

 you ascend the stem. 



CLASSIFICATION OF SWEET PEA. 



Class. — Dicotyledon. 

 Division. — Polypetalae. 

 Sub-division. — Calyciflorae. 

 Order. — Leguminosoe. 



Leaves, usually compound and stipulate. 



Flower, irregular. 



Corolla, papilionaceous. 



Stamens, ten. 



Carpel, superior and solitary. 



Fruit, generally a Legume. 



Seed, without endosperm. 



