108 



Salad Crops 



ing from the broad midrib ; stem leaves similar in shape to 

 the root leaves of the particular variety, alternate, clasping- 

 auricnlate, mostly finely apiculate-serrate, passing into bracts 

 toward the inflorescence: flower-heads erect, on short or long 

 pedicels, about 12- to 16-flowered, opening in morning and clos- 

 ing about midday, florets all perfect and each with a yellow 

 5-toothed ray ; receptacle naked ; involucre cylindrical, becom- 

 ing conical in fruit, scales lanceolate to ovate, all appressed, 

 the outer ones successively shorter ; ovary lenticular, bearing 

 many white pappus bristles at its constricted summit ; style- 

 branches short: acheue ("seed" of gardeners) white or black, 

 lenticular-oblong, broadest toward the top, strongly several- 

 nerved, bearing a long slender beak on which the pappus is 

 carried ; when the beak drops or is removed in threshing, the 

 remaining " seed " is % to in. long and weighs 1 to 1% mg., 

 retaining its vitality about 5 years. — Unknown in a native state 

 and considered to be a modification of Lactuca Scariola, Linn., 

 an Old World weed now also widely spread in this country. 

 In lettuce fields " rogues " now and then occur strongly sug- 

 gestive of L. Scariola. Lettuce has been cultivated so long 

 that its history is inexact. Yar. capitata, Linn. Sp. PI. 795 

 (L. capitata, DC, Prodr. vii, pt. i, 138. 1838). Head Lettuce, 

 has radical leaves forming a more or less dense ball. Yar. 

 crispa, Linn. Sp. PI. 795 (L. crispa, DC. I.e.). Curled Lettuce, 

 has the leaves cut and fringed or crisped. 



Yar. longifolia. Lam. Diet, iii, 403. 1789. (L. romana, Gar- 

 sault, Trait. PI. et Anim. Usage Med. ii. 196, t. 315. 1767.) Cos 

 Lettuce. Romaine Lettuce. Plant forming an upright col- 

 umnar or loaf-shaped loose head, the radical leaves obovate to 

 oblong, rounded or obtuse, 8 to 12 in. long and 4 to 6 in. broad, 

 the midrib usually very wide; stem leaves long, mostly oblong 

 or obovate, obtuse. 



Yar. angustana, Irish, Cyclo, Amer. Hort. 867. 1900; Bailey, 

 Gent. Herb. 1 :49. 1920, with botanical diagnosis. {L. angustana, 

 Hort.). AsPAEAGUS Lettuce. Plant not forming a compact 

 head : radical and lower stems narrow- or oblong-lanceolate, 

 long-attenuate, entire or irregularly sinuate-dentate, plane, 8 



