72 OBJECT LESSONS IN BOTANY. 



129. "With a sharp knife let us make a cross-section (that 

 is, a cut square across) of a flower-bud just ready to open ; 

 we may thus obrain some such views as are here drawn. 

 For example, in Fig. 217, we have the valvate arrangement. 

 Here the pieces composing the circle barely touch each other 

 by the edges, as in the sepals of Mallows, petals of Lilac, 

 valves of a seed-vessel. (See, also, Figs. 218, 219.) 



130. In the Phlox, Flax, Oleander, we find a twisted or 

 contorted arrangement of the petals (Fig. 220), where each 

 piece overlaps the next, all in one direction. 



131. The bud is said to be imbricated, when some of the 

 pieces are wholly outside, covering by the two edges others 

 which are wholly inside. But this may take place in various 

 ways. See how it is in the petals of the Eglantine, or Apple 

 (Fig. 221). Here two petals arc outside, two inside, and one 

 partly both. In the Tulip, one sepal is outside, one inside, 

 and one partly both. And just so with its three petals 

 (Fig. 222). 



132. The bud is convolute when each leaf wholly involves 

 all that are within it, as do the petals of Magnolia and Wall- 

 flower (Fig. 223) ; and it is vexillai^ in the Pea tribe, where 

 only the outside petal, larger than the rest, infolds them all 

 (Fig. 224). 



133. The plicate arrangement is found in monopetalous 

 flowers, as in Thornapple, Potato, where the corolla is folded 

 in a manner somewhat like a fan. 



129. How do we prepare a bud for examination ? What do you under 

 stand by a cross-section ? Define the valvate arrangement, with examples. 



130. "What aestivation do we find in Flax, Phlox, &c. ? 



181. What is the imbricated aestivation? Describe it in the petals cf 

 Tulip ; Apple ; Eglantine. 



132. How are the petals arranged in the bud of Wall-flower ? 



133. How in the flower of Thornapple? or Potato? 



