SYM PETALS. 505 



adnate to it, the ovules have only one thick integument and a small 

 nucellus. (The exceptions are noted later.) 



This Sub-class is no doubt more recent than the Choripetalae ; it is also 

 peculiar iu including fewer trees and shrubby forms than the latter. 



The SjmpetaliB may be separated into 2 sections : 



A. PENTACYCLIC^: (FIVE-WHORT.ED). The flowers in this section 

 have 5 whorls equal in number, namely, 2 staminal whorls in addi- 

 tion to the calyx, corolla, and carpels ; in some instances, one of 

 the staminal whorls is rudimentary or entirely suppressed, but in 

 this case it is frequently the sepal-stamens which are suppressed, 

 and the whorl which is present stands opposite the petals. The 

 flowers are regular. The number of carpels equals that of the 

 sepals, but in one of the orders (Bicornrs) they are opposite the 

 petals (the flower being obdiplostemonous) ; in the other two 

 orders (Primulinte and Diospyrinai) they are placed opposite the 

 sepals (the flower being diplostemonous). This section is the 

 most closely allied to the Choripetalse, since the petals may some- 

 times be found entirely free, and the stamens inserted directly on 

 the receptacle (Ericacea?) ; ovules with two integuments are also 

 found. It is very doubtful, whether the orders included under this hea.l have 

 any relationship with the other Syinpetalae. They appear in any case to repre- 

 sent older types. 



B. TETRACYCLIC^; (FOUR-WHORL ED). The flowers have only 4 

 whorls, namely, beside sepals, petals, and carpels, only one whorl 

 of stamens, which alternates with the petals ; there is no trace of 

 the second staminal whorl, and when the number of carpels is the 

 same as that of the preceding whorls ( " isomerous ") they alternate 

 with the stamens ; but in most cases there are 2 carpels placed in the 

 median plane (see the diagrams, e.g. Figs. 559, 567, 583, 590, etc.). 

 This section is the largest, and the one which shows the character- 

 istics of the Sympetalas best. Very irregular flowers are met with. 



The following families belong to the Pentacyclicae -. 26, 

 Bicornes ; 27, Diospyrinpe ; 28, Primulinse. 



The remaining families belonging to the Tetracyclicae are : 



a. HYPOGYNOUS flowers (with a few exceptions) : 29, Tubijlorse ; 

 30, Personatte ; 31, Nuculiferae ; 32, Gontortae. 



b. EPIGYNOUS flowers: 33, Rtibiales ; 34, Dipsacales ; 35, Cam- 

 panulinse ; 36, Aggregates. The ovaries and ovules in the last 

 family are always reduced to one; and at the same time the 

 fruits become nuts, and the flowers are united into crowded 

 inflorescences. 



