94 THE STORY OF PLANT LIFE 



tribe are in one row, the radicle is incumbent, 

 lying on the back of one cotyledon, or parallel 

 with the faces of the seed-leaves, straight and plano- 

 convex. The other types are the Hedge Mustard and 

 Dame's Violet. In Treacle Mustard the hairs are 

 closely pressed, and forked two or three times, with 

 a blunt stigma. 



In the third tribe, or Cabbage tribe, we have 

 selected White Mustard as a type. In this tribe 

 the seeds are in one or two rows ; the radicle is 

 incumbent, folded lengthwise, or concave. The 

 Rockets are the other members of this tribe. In 

 the Cabbage group the pods are round in section, 

 or angular. The seeds are in one row. 



The second main group, or Siliculosse, comprises 

 the Crucifers in which the pods are not, or not 

 much, longer than broad, and open throughout their 

 whole length, being broad, flat or swollen, not 

 flattened at right-angles to the septum, which is 

 broad. But, as has been seen, the pod is longer 

 in Whitlow Grass. 



The Siliculosae include two other tribes, in which 

 the septum is narrow. The pods are also indehiscent 

 in the third group, with Siliculose pods, and the 

 valves are very short in Isatis, or are tomentose, as in 

 Crambe, Cakile, and Raphamis. 



In the Sweet Alyssum tribe the seeds are in two 

 rows, and the radicle is accumbent. It includes 

 Whitlow Grass, and Erophila, of which we have 

 included Vernal Whitlow Grass as a type, Alyssum 



