324 THE LOWER DICOTYLEDONS. 



middle, like a compass-needle; they are well adapted for 

 preventing slugs and snails from crawling over the plant. 

 Tear off a strip of skin (epidermis) from stem or leaf, mount 

 in water, and draw some of the hairs seen with the microscope. 

 In a raceme note that all the flowers are at first kept 

 nearly at the same level, owing to the longer stalks of the 

 lower flowers, but as the lowest flowers wither (after pollina- 

 tion) the raceme-axis grows on and the next flowers to open 

 take their places, until all the flowers have opened and been 

 pollinated, then the axis keeps on lengthening and spaces out 

 the fruits. Note the position of each part of a flower with 

 reference to the stem or raceme-axis (Fig. 126). 



Note the four free erect purplish sepals, in two pairs, one 

 pair (right and left) a little below (outside) the other (front 

 and back) pair ; the two lower (outer) sepals are bulged at 

 the base. Note the four free petals, each with a narrow erect 

 lower part (claw) and a broad spreading upper part (limb) ; 

 the two outer short stamens (one opposite each of the bulged 

 sepals) and the four inner long ones (in two pairs, a pair 

 opposite each inner sepal) ; the cylindrical ovary with two 

 rounded stigma-lobes on a very short style ; 

 the green nectaries at the bases of the 

 outer stamens. 



The honey can only be reached by fairly 

 long-tongued bees and butterflies ; they 

 stand on the platform made by the 

 spreading petal- limbs. In probing for the 

 honey, which collects in the pocket-like 

 bases of the outer sepals (each of the two 

 outer stamens stands out, leaving a space 

 Fig 127 Floral Dia- between it and the pistil), a bee will rub 

 gram of a Crucifer. against an anther with one side of its head 

 and against the stigma with the other side. 

 The fragrant flowers are much visited by bees and butterflies, 

 but are self-pollinated in the absence of insect-visits. 



The structure of the ovary is best seen by examining the 

 fruit or " pod " into which it grows ; it can, however, be 

 made out with a lens. The ovules are attached to the inner 

 wall of the ovary at opposite sides (front and back), but 

 from each placenta a plate of tissue grows (when the flower 

 is developing) to meet a corresponding plate from the opposite 



