214 GENERAL BOTANY 



of which are tubular, but in the outermost ones the 

 whole corolla is extended as a long yellow flat tongue. 

 Such florets or flowers are termed ligulate (tongued), 

 for there is no upper lip. The same is the case in 

 Zinnia, while in the Chrysanthemum and Dandelion 

 all the florets are ligulate. 



At first sight there may not seem to be much differ- 

 ence between a lip and a ligule. But the word 

 lip (or labellutn sometimes) is used when a part only 

 of the corolla is so extended while part forms an 

 upper lip, ligule, when the whole is expanded on one 

 side, so that there is no upper lip. 



THE ESTIVATION 



6. On examining flowers of different plants, we 

 soon find that there are differences not only in the 

 number and shape of the parts, but in the way in 

 which the petals are folded together in the bud. 



We have already seen that in CASSIA and in POIN- 

 CIANA the posterior petal is innermost, while in 

 CROTALARIA and PHASEOLUS, it is outermost. Each 

 plant, or rather each family or group of plants has 

 its own method of folding the petals, and the peculiar 

 mode in each case is termed its aestivation. 



In some the petals (or corolla lobes) just touch 

 by their edges, and do not overlap each other at all. 

 They are then said to be valvate. 



In others each overlaps the next on one side, being 

 in turn overlapped by the one next it on the other. 

 The petals then generally slope to one or the other side,, 

 the whole bud appearing for this reason to be twisted, 

 They are then said to be convolute or twisted. 



