SWEET PEA STUDIES — III 

 CULTURE OF THE SWEET PEA 



Alvin C. Beal 

 PART I. THE GENUS LATHYRUS 



BOTANY OF THE GENUS 



The genus Lathyrus (a name used by Theophrastus for some leguminous 

 plant) belongs to the important family Leguminosae, which embraces 

 three suborders, eighteen tribes, and one hundred and twenty-seven 

 genera of plants cultivated in North America. The suborder Papilioneae 

 is distinguished from the suborder Mimoseae in having irregular or 

 zygomorphic flowers, and from the suborder Caesalpineae in having 

 papilionaceous flowers ■ — ■ that is, the standard outside the other petals, and 

 enclosing them in the bud. 



Among the most important genera that contain ornamental plants are 

 Thermopsis, Lupinits, Laburnum, Genista, Cytisus, Cladrastis, Hedysarum, 

 Lespedeza, Lotus, Dolichos, Pueraria, Erythrina, Apios, Centrosema, 

 Wisteria, Robinia, Clianthus, Swainsona, Caragana, and Glycyrrhiza. 

 Then there are the genera of economic importance, Arachis, Onobrychis, 

 Desmodium, Vicia, Pisum, Lens, Phaseolus, Vigna, Mucuna, Glycine, 

 Trifolium, Medicago, Melilotus, and Indigofera. 



The plants of the tribe Vicia, which includes the genera Abrus, 

 Lens, Vicia, Pisum, and Lathyrus, are typically climbing herbs, with 

 evenl}'- pinnate leaves, which raise them.selves by m.eans of tendrils 

 at the tips of the petioles. The varieties of Phaseolus, the other tribe 

 of typically climbing herbaceous plants, have twining stems and three 

 leaflets. 



Abrus differs from the other genera of this tribe in having woody stems, 

 and nine stamens instead of ten. Lens (lentil) has flowers with the wings 

 adherent to the keel. Vicia (vetch), Pisum (pea), and Lathyrus are 

 closely allied and somewhat difficult to distinguish. Vicia is usually 

 known by the sheath of the stamens being oblique at the mouth, and the 

 style being slender and bearded at the apex or only around the upper 

 part ; Pisum and Lathyrus have the stamen sheath even at the mouth, but 

 are distinct from each other in that in Pisum the calyx lobes are leafy 



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