380 ELEMENTARY STUDIES IN BOTANY 



The earliest varieties develop in about three months from 

 seed, and the later varieties extend this period up to six or 

 seven months. The seeds are sown in boxes in the usual 

 rows, and then transplanted into the permanent bed. If they 

 are to be set out in March, the seed is started early in Feb- 

 ruary. For later crops the seed is sown out of doors in a well- 

 prepared germination bed, which is repeatedly raked to hold 

 moisture until the plants are removed to their permanent 

 place. 



87. Lettuce. This is the most popular salad vegetable 

 and grows so quickly that it should be one of the forms used 

 in school work. It belongs to the largest family of flowering 

 plants (Composite), a family which is also the highest in 

 rank, which means that it is regarded as the most highly 

 organized family in the plant kingdom. Some of the familiar 

 associates of lettuce in this great family are such ornamental 

 plants as golden-rods, asters, daisies, sunflowers, dahlias, 

 and chrysanthemums ; such weeds as ragweed, cocklebur, 

 thistle, and dandelion; and such useful plants as chicory 

 and artichoke. 



The family is characterized by its compact head of flowers, 

 which is thought of by most persons as a single flower (Fig. 

 61). But if the so-called flower of dandelion or sunflower be 

 examined, it will be discovered that it consists of numerous 

 very small flowers packed together upon a flat disk (receptacle) , 

 and the whole assemblage of flowers surrounded by a rosette 

 of small leaves (involucre) . 



There are two general types of lettuce in cultivation : 

 (1) head lettuce, which heads up like cabbage, and (2) loose 

 lettuce. The latter is more used because it is grown more 

 easily, but the former is regarded as the finer. Since the 

 value of lettuce depends upon its freshness, it is grown almost 

 universally in home gardens, and a very small area yields 

 enough to supply a family. There is no vegetable grown so 

 easily in sufficient quantity in city backyards. The proper 



