THE CRUCIFEROUS TRIBE. 59 



plants belong to an extensive tribe called Cruciferous, 

 or Cross-bearers, because their four petals are placed 

 in such a way as to resemble in some degree a Mal- 

 tese cross. Unfortunately for those who have little 

 power of observation, and less patience, their flowers 

 are usually very small ; but I am convinced that this 

 circumstance will be far from deterring my young 

 friends from attempting their study ; it will rather 

 operate as an incentive to their making themselves 

 acquainted with them. 



They are already, I suspect, familiar with a mean- 

 looking weed, called Shepherd's Purse (Capsella Bursa 

 pastoris), which is found every where at all seasons of 

 the year, except the severest part of the winter. Its 

 name was given it because it has a number of pouches 

 filled with very small seeds, which you might fancy 

 were fairy coins. Let us look at it botanically. 



Its leaves are veined in that netted manner which 

 indicates the Exogenous structure ; and consequently 

 you know that if it were ever to form a woody stem, 

 its woody matter would be arranged in concentric 

 circles. The form of the leaves is like that of an 

 ancient arrow head, sitting closely to the stem, and 

 extended downwards at the base into a sharp barb on 

 either side (Plate IV. 1.). 



The flowers are arranged regularly upon a central 

 stalk in the form of a raceme ; and, what is extremely 

 singular, they are uniformly destitute of bracts. This 

 is so unusual a case that I do not remember any 

 other instance in the whole vegetable kingdom in 

 which bracts are so constantly absent ; the absence of 



