::: 



SCIEXCE-GOSSIP. 



temperature being required for the completion of 

 maturation than for the flowering and the early 

 stage of the fruiting process. And after a careful 

 comparison of my river and pond temperatures, I 

 formed the conclusion that whilst in water twelve 

 to eighteen inches deep this plant requires for a 

 week or more an average daily maximum tempera- 

 ture of seventy degrees Fahr. to produce its 

 flowers, a warmth of eighty degrees and over is 

 necessary to mature its fruit, a condition to be 

 found in this country in shallow ponds, where the 

 plants may fruit abundantly, but not in rivers, 

 where they flower, but do not, as far as I know, 

 mature the fruit. The thermal conditions for the 

 maturation of the fruit can occur only in our 

 shallow ponds ; those for the flowering alone are 

 found in our rivers. (Proc. Roy. Phys. Soc., Edin. 

 xii., p. 296.) 



In this climate, according to my observations, 

 the plants propagate themselves in the spring 

 :b:ed; z arddary buds z~ ::.; z'.i s:e~s ar.d bv 

 the budding of detached portions. Through the 

 winter the brown unattached stems of the past 

 season can be seen lying on the mud in the 

 shallows of ponds and rivers. Though they are 

 but slightly heavier than the water, and are easily 

 borne along by a sluggish stream, the mud that 

 collects on them, and the living freight of aquatic 

 molluscs, insects and annelids stowed away 

 amongst their leaves, keep them at the bottom all 

 the winter. In April they begin to produce fresh 

 green shoots from buds in the axils of their leaves, 

 and commence to grow at their extremities. The 

 new stems and branches grow rapidly, and, being 

 themselves buoyant, the whole plant gradually 

 assumes the vertical position, and by the middle of 

 May, when it is, perhaps, fifteen or eighteen inches 

 long, it floats upright with the old brown stem of 

 the previous year trailing on the mud, or partially 

 covered in it, whilst the new growths tip the 

 surface. With the flowering in June and July, the 

 old year's stems will be found to have decaved 

 away, leaving the shallows more or less filled by 

 the present year's growths. On the approach of 

 autumn the mass of the plant, so dense in the 

 summer, diminishes greatly, and through the 

 agencies of gales and floods large quantities 

 become detached and are carried down the stream, 

 or scattered about the pond. As the winter comes 

 on they get stranded in the shallows, where, coated 

 with fine mud, and affording shelter to a multitude 

 of aquatic organisms, they pass the season ready 

 for the spring. Floating, through the winter to 

 the spring, amongst the seed-drift of our ponds 

 and rivers occur small fragments of the plant, 

 usually from half-an-inch to one-and-a-half inch 

 in length, and produced in the autumn by the 

 death of the stem or branch except at the 

 extremity. These small floating portions develop 



from axillary buds new plants in the spring. They 

 do not withstand ice well, and in this respect are 

 much inferior to similar portions of Myriophyllum 

 that also float through the winter in river and pond 

 drift. An inclosure of five or six days in ice kills 

 most of them, only a few recovering and growing 

 healthily. 



I will next refer to the conditions of temperature 

 requisite for budding and growth in the spring. 

 In the case of a number of floating portions kept 

 under observation all the winter, I estimated the 

 temperature necessary to produce the growth of 

 the axillary buds at fifty-three degrees, which was 

 the mean of the previous five or six days in a room 

 where the daily range of water-temperature was 

 only five or six degrees, the temperature previous 

 to this period having been always cooler. I did 

 not find that the old stems lying at the bottom of 

 the Home Park pond showed growing buds in 

 their axils, until the temperature of the water had 

 risen to sixty degrees in the daytime for about a 

 week. Allowing for the daily range, this gives a 

 mean of fifty-seven degrees ; however, I will take 

 df-v-uve i~i - rees due ~ rir. :: :br iud::r aud zzzzz. 

 estimates, as the temperature at which the plant 

 buds e.:.: rr:~= :r_ due -:::-: 



Ibis -s.rtr ::r. d.udes vd:b a :ab'.e :i :euTuera:urts. 

 in which Ceraiophyllum demersum is compared with 

 species of Myriophyllum, plants which I have worked 

 at on the same lines. Our Myriophylls also pro- 

 pagate themselves in the spring by the growth of 

 the last year's stems, and from free budlike portions 

 that pass the winter either afloat or at the bottom, 

 active growth being announced in both cases by 

 the appearance of roots at the bases of the lower 

 leaves. Roots, as I have before observed, are not 

 to be found in CeraiophyUum. The experiments on 

 these two plants were carried out under the same 

 conditions and often in the same vessel, a marked 

 difference in the estimates of the budding and 

 sembuatiug :e~uera:ures ber.vetu due v : :dau:s 

 corresponding to a considerable difference of time 

 measured in weeks. To endeavour to illustrate all 

 the complexities of pond-temperature in this table 

 would be impossible, and to attempt to explain some 

 of the apparent inconsistencies would require an 

 adequate treatment of the Myriophylls, for which 

 there is no space here. It may be remarked that 

 the estimates of the mean temperatures of ger- 

 mination and budding and of the maamnm tem- 

 reravures ::' d :::u aud :ru::iu; are :r;~ iirec: 

 observation at home and in the ponds. The other 

 elements are supplied from the acquaintance, which 

 a large number of observations have given me, 

 with the thermal economy of a pond in different 

 seasons of the year. The thermometric data for 

 : phyllum axe based on two years' results which 

 c'.zsi'.y arrtri ;b:se ::r d. .:::: '_ -..'.'; . are fbuuded 

 mostly on those of one year. 



