84 FLORA'S CLOCK. 



occur with the same regularity, and when vegetation is injured 

 by any circumstance, it may have barren years. It has also 

 been observed, that when a tree has borne a great deal of fruit 

 one year and retained it late, inflorescence is feeble or entirely 

 wanting the succeeding year; and thus it is in the south of 

 Europe, when the olives are left late upon the trees, the harvest 

 fails the following year. Sometimes, on the contrary, the periods 

 of inflorescence are more approximated, and in warm and humid 

 autumns, we occasionally see plants flowering a second time. 



4. The period of the year at which inflorescence takes place 

 is generally definite for each species of plant, but varies a little 

 according to the temperature and other atmospheric circum- 

 stances. For example, in the climate of Paris (which is similar 

 to that of the Middle States), the black hellebore flowers in 

 January ; the hazel tree and willow in February ; the box, the 

 yew, the almond, the peach, the apricot, the primrose, the stock- 

 gilly flower, in March ; the plum, the pine, the ash, the elm, the 

 yoke-elm, the hyacinth, the dandelion, &c., in April ; the apple, 

 the horse-chestnut, the lilac, the cherry, the peony, in May ; the 

 linden tree, the vine, oats, wheat, the wild red poppy, larkspur, 

 in June ; the violet, the carrot, hemp, lettuce, in July ; asters, 

 garden-balsams, and water-hyssop, in August; ivy, saffron, in 

 September; Jerusalem artichoke and certain other plants, in 

 October. The table of the different epochs of inflorescence con- 

 stitutes what botanists have named Flora's calendar. In colder 

 countries, inflorescence is retarded, while in the South it occurs 

 earlier ; for example, in Smyrna, the almond flowers in the first 

 fortnight of February ; in Germany, in the second half of April ; 

 and in Christiania (Sweden), in the first days of June. 



5. The expansion or blooming of the flower is 

 almost always effected by the separation of the 

 pieces of the corolla and calyx from above down- 

 wards; but there are some in which the floral in- 

 teguments remain adherent to the summit, and 

 separate at the base, as in the vine, for example 

 (fig. 115). 



6. The period of the day at which this phenomenon occurs 

 varies in the greatest number of plants, but in some it is fixed, 

 and a series of plants arranged according to the hour at which 

 the flowers blow, constitutes what Linnaeus called Flora's clock. 

 For example, at Paris, the bearbind (a species of bind-weed) 

 blows between three and four o'clock in the morning ; between 



4. Does inflorescence recur in the same species of plant at the same 

 period ? What is meant by Flora's calendar ? 



5. How does a flower expand ? 



6. What is meant by JFlora's clock ? 



