THE GROWTH OF THE SHOOT FROM THE T3TJD 55 



go-to-bed-at-noon opened from three to five in the morning and 

 closed from eight to ten ; the Mouse-ear Hawkweed, he says, is 

 open in fine weather from seven in the morning until three in the 

 afternoon. 



Another order, in which an involucre of bracts is often though 

 not always found, is the Umbelliferae. One of the most beautiful 

 species is Astrantia, in which the bracts are white and shining, 

 looking silvery in the sunlight ; they are far larger than the 

 flowers themselves. In the Sea Holly the bracts are also coloured 

 and conspicuous. When the wild carrot is in bud, the long 

 green bracts arching over the umbel, form a great protection 

 for the young flowers. In the Arum (lords and ladies) the 

 conspicuous bract (Fig. 44) forms a chamber in which the flowers 

 are situated and to which insects are enticed. Many hothouse 

 plants, natives of tropical regions, have very conspicuous coloured 

 bracts. The Poinsettia and the Bougainvillea are plants growing 

 in the open air in the tropics, they are commonly seen at flower 

 shows in this country ; the one has a large leaflike scarlet bract, 

 the other purple bracts forming a cup around the flower. 



The observations that may be made on leaves are practically 

 unending, only a few can be indicated here. 



(a) The arrangement of leaves, whether radical or cauline. 

 If the latter, whether they are spread out to the light, or merely 

 present their edge to the sun's rays. Again, their relative position 

 to each other, so as to secure light. 



(&) The endless variety of shape, and the connection of this 

 with the habitat of the plant. 



(c) The general structure of the leaf ; note any marked differ- 

 ence between the two sides, one much darker than the other. 

 See whether leaves in which the chlorophyll is evenly distributed 

 are connected with any particular habitat, as Stonecrop with dry 

 situations. Make notes on the habitat of plants with hairy leaves, 

 or leaves that roll in to protect the stomata. These will often be 

 found in grasses growing by the sea. 



(d) The difference in bud-scales of different trees and different 

 herbaceous plants may be noticed. The scales of the winter buds 

 of trees are particularly interesting. 



(e) The sensitiveness of leaves, e.g. Wood-Sorrel, Mimosa. 



