IRISH GARDENING. 



99 



point, and closingf ag-ain in a dull lig-ht or in 

 darkness. Strong;, direct sunlight will, however, 

 cause some flowers (marigold, for example) to 

 close. 



This opening- and closing- of the flower is an 

 act associated with the normal g-rowth of the 

 petals. If the upper side is expanding and 

 the growth of the lower side stopped, then of 

 course the petals will move outwards and the 

 flowers will open, while the converse happening 

 the flower will close. So much has been proved, 

 but ivhy moisture or the lack of it, or tempera- 

 ture or light in varying intensities, should make 

 one side of the petal grow and the other not are 

 matters we know, at present, little or nothing 

 about. 



These being the chief factors influencing 

 the periodical opening and closing of flowers, and 

 remembering that different plants vary in degree 

 of response to these stimulating influences, 

 it is very easy to understand why many flowers 

 open at different hours of the day and have 

 regular successive closing times, as the intensity 

 of the sun increases and the temperature of the 

 air rises in the morning, and the one slackens 

 and the other gradually falls towards the evening. 

 Then, again, this periodicity gets more or less 

 impressed on the constitution of the race as is 

 shown in the feeble attempts of certain flowers 

 to open or close at the " right " hour if they are 

 kept under uniform conditions as to darkness or 

 temperature. 



It is interesting to observe and keep records 

 of such periodicity in the opening and closing 

 of flowers ; and long ago, Linnaeus and, 

 since his time, many other botanists have con- 

 structed "floral clocks," by means of which the 

 approximate hour of the day can be told by 

 observing the exact time of the opening and 

 closing of particular blooms. We need only 

 mention a few to illustrate our point. The 

 goat's beard, now in blossom, opens its head of 

 bright yellow flowers at sunrise and closes them 

 again at noon ; hence its other common name of 

 Jack-go-to-bed-at-noon. The common centaury 

 also opens at sunrise and, at least partially, closes 

 by three in the afternoon, but it is so sensitive 

 to light that it rarely opens at all if the days are 

 dull or cloudy. The dandelion opens about four 

 o'clock in the morning, and the smooth hawk's- 

 beard of cottage roofs [Crepis virens) about 

 five. Scorzonera, another "composite" plant, 

 opens at the approach of six o'clock, while 

 between six and seven various kinds of sow 

 thistles and hawkweeks slowly unfold. Exactly 

 at seven the common lettuce, and at eight, if the 

 weather be suitable, the scarlet pimpernel 

 spread their petals to the morning sun. Venus's 

 looking glass {Spccularia speciihivi) of our 

 gardens opens some time between these two 

 hours. 



Then comes the opening of the flowers of 

 purple Savin {Junipenis mbind) at ten, and the 

 Star of Bethlehem {prnithogalum timbeHafnm) 

 at eleven. This last named plant is indeed 

 frequently called the " Eleven-o'clock-lady" by 

 gardeners. One hour after mid-day finds the 

 flowers of succory just opening, and at two the 

 squill hyacinth. The marigold is an uncertain 

 " riser" at three, while the "F'our-o'clock-flower" 

 of our gardens {Mtrabilis dichotomci) is well 

 known. It is not until five or six o'clock in the 

 evening that the flowers of the sweet-scented 

 night-flowering Catchfly {Silene noctiflora) open 

 to let free their delicious perfume. Following 

 these come the evening primrose, which after 

 about half-an-hours' struggle with the enclosing 

 sepals the flower suddenly bursts open at about 

 six o'clock. Lastly, growers of Cacti know 

 that the night-flowering cereus {Ceretis nocti- 

 florus) begins to open its glorious flowers about 

 eight, and is in full bloom by midnight. This 

 list could of course be considerably extended, 

 but sufficient has been said to illustrate a par- 

 ticular section of plant study that is certainly 

 not lacking in interest to lovers of srradens. 



Photo, iy^ \T. Price. 



Branch of Gooseberry entirely defoliated by Saw-fly 



Caterpillar. 



