THE FLOWER AND INSECT-POLLINATION 155 



of the stamens is much less common (Fig. 108) ; and while 

 it is much more common in the case of the sepals, it is quite 

 irregular. 



It is petals, however, that deserve special attention, for 

 their growth in common or separately is a regular feature of 

 great groups. The various forms that these so-called " united 

 petals " assume are well known to all who notice flowers, as 

 the funnel-shaped corolla of the morning glory, the bell- 

 shaped corolla of the bell-flower, the nearly wheel-shaped 

 corolla of the potato or tomato flower, the tubular corolla 

 of the coral honeysuckle, etc. (Figs. 102 and 103). A corolla in 

 this condition is called sympetalous ( 81, p. 133). So constant 

 a feature is it of the families in which it occurs, that it gives 

 name to one of the two great groups of Dicotyledons, the 

 Sympetalce. The Sympetalse include all the higher families 

 of the Dicotyledons, and in distinction from them, all the 

 Dicotyledons whose flowers are not sympetalous are called 

 Archichlamydece, a name which means " primitive perianth," 

 and is intended to include not only flowers that have the 

 petals separate (polypetalous), but also those without petals 

 and even without a perianth. 



In this connection it may be pointed out that there are 

 three great groups of Angiosperms to remember : the Mono- 

 cotyledons and the two groups of Dicotyledons. They are 

 very easy to distinguish ordinarily by their flowers, for if a 

 flower has its members in threes, it is almost certain to belong 

 to a Monocotyledon ; if it has its members in fives or fours 

 and its petals are separate, it belongs to the Archichlamydeae ; 

 if the flower parts are in fives or fours and the corolla is sym- 

 petalous, it is one of the Sympetalae. 



96. Union of two or more sets. Not only do the members 

 of a single set often appear united in a flower, but two or more 

 sets may grow together more or less completely. It has been 

 mentioned ( 82, p. 136) that in the case of sympetalous corollas 

 it is usual to have the stamens develop in common with them r 



