SPERMATOPHYTES : ANGIOSPEKMS 



209 



several cotyledons in a cycle (Fig. 154) ; and in Dicotyle- 

 dons there may be one or three cotyledons ; but as a pair 

 of opposite cotyledons is almost without exception in the 

 group, it is named Dicotyledons. 



The axis of the embryo between the root-tip and the 

 cotyledons is called the hypocotyl (Figs. 154, 193, 194), which 



Fig. 181. Development of embryo of shepherd's purse (Capsella), a Dicotyledon: 

 beginning with /, the youngest stage, and following the sequence to VI, the old- 

 est stage, V represents the suspensor, c the cotyledons, s the stem-tip, w the root, 

 A the root-cap. Note the root-tip at one end of the axis and the stem-tip at the 

 other between the cotyledons. — After Hanstein. 



means " under the cotyledon," a region which shows pecul- 

 iar activity in connection with the escape of the embryo 

 from the seed. Formerly it was called either caulicle or 

 radicle. In Dicotyledons the stem-tip between the coty- 



