480 Notes and Memoranda. 



Mollusca." He attaches great importance to the heart and to the organs of repro- 

 duction. He says, " The development of the young is of less systematic value than 

 is generally believed : this is proved in the Crustaceans, the marine species having 

 a larval form very different from the fluviatile species {Astacus Jluviatilus, A. 

 Marimis) ." 



Temperature at which Plants Germinate. — M. Alp. De Candolle read at 

 the August meeting of the Societe Helvetiques des Sciences Naturelles a paper on 

 the above subject, detailing the results of many experiments. We extract a few- 

 particulars from the Archives des Sciences, No. 95. "White mustard (Sinapis 

 alba) will germinate below 0° (the freezing point of the Centigrade scale) ; a flax 

 plant (Lepodium) germinated at a mean temperature of l° - 8 C, rather more than 

 36° F. Collomia does not germinate below 3° C, but will do so below 5 0- 3 C, or 

 just below 42? F. Nigella, Iberis, and Trifolium repens did not germinate at the 

 last named temperature, but did at 5°'7 C. Maize germinated below 9° C. or 4S° - 2 F., 

 but not below 5 0, 7 C. Sesamun germinated at 13" C, or 55M F. Melon seed 

 would not germinate at 13° C, but did below 17° O, or 62° - 6 F. Seeds will not 

 germinate above certain temperatures, varying with their species and the amount 

 of moisture present ; thus the greater part of some Trifolium repens seed 'did not 

 germinate above 28° C, or 82 0- 4 F. Thus seeds only germinate between certain 

 limits of temperature, and those which can only do so within nai'row limits are 

 least able to extend themselves geographically. Seeds of the same kind and 

 origin will sometimes germinate in succession and not simultaneously. M. De 

 Candolle says, that germination may be explained without any reference to 

 " vital force," which he " leaves to the poets." The actions are, he states, " solely 

 physical and chemical ;" " the young plant in the seed, is like a prisoner confined 

 in a small space. Physical and chemical causes enlarge the boundaries of its 

 prison, render them flexible and permeable, and sometimes transform encumbering 

 matter into nutritive liquids." If these operations proceed with neither too 

 great nor too little force the plant grows. 



The Temperature oe Birds. — Dr. Davy has an important paper on this 

 subject in Proc. Roy. Soc, No. 78. He thinks that the respiration of birds is 

 less active than is commonly supposed, and their high temperature is maintained 

 by their warm clothing, and by the small loss of heat they experience through 

 pulmonary or cutaneous evaporation, which is small in their case. 



Food of Larks. — In the paper just mentioned, Dr. Davy states that he has 

 always found grass in the gizzard of larks in the winter, and he regards it as their 

 chief food at that season. 



" The Eart"h in the Comet's Tail." — Our readers will recollect this 

 was the title of a paper in our vol. i. p. 63, in which Mr. Webb furnished, from 

 his own observations, reasons for corroborating the conclusion arrived at by Mr. 

 Hind, that on the evening of June 30th, 1861, or a little earlier, our earth was 

 in the tail of the comet then visible. M. Liais at the same time thought we had 

 actually passed through the second tail of this comet. He now states, in Comptes 

 Hendus, that more complete calculations confirm this belief. He computes that 

 the axis of the second tail of the comet must have cut the earth's orbit at 

 6h. 12m. 10s. in the morning of the 30th June, at Eio Janeiro, and at that time 

 he considers that we were plunged 110,000 leagues deep in the tail. From the 

 velocity of the earth's motion he estimates that our entrance into the tail was 

 four hours earlier. Rio Janeiro is in long. 43° 7' 15" west of Greenwich. M. 

 Liais adds that if, as certain European observers thought, the tail was a little 

 curved, we might, instead of simply passing through it, and across it, have 

 moved for some time in the direction of its long axis. The breadth of the tail he 

 estimates at 878,000 leagues. 



