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HARDWICKE'S SCIEN CE -GO SSIP. 



of the animal-eating mollusks ; I therefore conclude 

 the Pleurobranch is a vegetarian ; yet I should like 

 to join my request to Mr. Sclater's, to see the 

 opinion on this subject, of some one of more exten- 

 sive experience, if there is still a doubt on the 

 question, in Science-Gossip. I do not care to have 

 extracts from books, but practical experience, and 

 for some reasons I have in reference to this same 

 Pleurobranch,— e.g., I was partly led on to examine 

 this mollusk and extract its palate through reading 

 the interesting book "On Objects for the Micro- 

 scope," by L. L. Clarke, wherein I read his descrip- 

 tion of the palate of the Pleurobranch, which, so 

 arrested my notice that I became exceedingly in- 

 terested in it, and, after prolonged effort to obtain 

 one, I was amazed to find the author had described 

 the gizzard for the palate ; and, consequently, the 

 palate really was not noticed. I presume he was 

 misled by a slide mounted by some other person 

 than himself, and then misled his readers through 

 its being wrongly named. — /. Turner. 



BOTANY. 



The Botany and Geology of West York- 

 shire.— Dr. P. A. Lees, and J. W. Davis, F.L.S., 

 are engaged upon a complete description of the 

 Geology, Botany, Physical Geography, &c, of the 

 West Riding of Yorkshire, and the book (which 

 will be a large one, and limited in impressions) will 

 shortly be published. 



Symphytum: tuberosum. — This is a common 

 plant in the vicinity of Edinburgh, and S. officinale 

 is also found, but in less abundance. Now I wish 

 to point out what appears to be a mistake about 

 the time when these two plants are in flower. Many 

 of our Floras give May and June as the flowering 

 season of S. officinale, and June and July as that of 

 tuberosum. But my own observation of t he plants 

 leads me to consider this a mistake. During the 

 present season S. tuberosum was in flower from 

 about the middle of May till the middle of June. 

 But officinale did not begin to flower till about the 

 middle of June, and continued flowering till August. 

 Perhaps some of the readers of Science-Gossip 

 may have observed which of the species is first in 

 other localities. — D. Douglas. 



Direction of Plant-growth. — The direction 

 of plant-growth, it is known, is determined both by 

 light and by gravity. The geotropism, or action of 

 gravity exclusive of light, has before been examined ; 

 and recently M. Mullcr, of Thurgau, has en 

 deavoured to study the converse fact of heliotro- 

 pism, by excluding the influence of gravity as far as 

 possible. He grew his plants in a cylinder rotating 

 about its horizontal axis. The apparatus was so 



arranged that the light, coming through an aperture 

 in the shutter of a dark room, fell parallel to the 

 axis ; the bendings observed were thus purely 

 heliotropical. Among other results he found that 

 only those zones which were not fully grown out, 

 showed heliotropic bendings ; that the most 

 strongly growing parts of the stem were most 

 sensitive to one-sided illumination ; that the bend- 

 ing takes some (variable) time to manifest itself 

 and continues some time after removal of the cause ; 

 that the rate of bending is at first slow, gradually 

 increases to a maximum, and thereafter diminishes ; 

 that the bending is greater the intenser the light* 

 &c. 



Germination of Seeds. — It has recently been 

 proved that several kinds of seeds will germinate 

 between pieces of ice. A full investigation of the 

 lowest limit of temperature at which plants may 

 germinate has just been made by M. Haberlandt. 

 The experiments were upon wheat, rye, barley, red 

 beet, rape, lucern, poppy, and mauy other seeds. 

 Several hundred seeds were ''employed of each 

 species, and every fourteen days the seeds were 

 taken out of the ice-chest, whose temperature was 

 kept constant between 0° and 1°, and examined in a 

 space whose temperature was under freezing-point. 

 In forty-five days a decided beginning of germina- 

 tion was observable in eight different species. In 

 four months it had continued to progress in a 

 minority of these ; the rest had stopped. In 

 fourteen species there was no germination. 

 M. Haberlandt is of opinion that those seeds 

 which can germinate at a lower temperature than 

 others of the same species, will give plants that 

 require a less amount of heat for their complete 

 development than the others, and thus by artificial 

 sowing in cold spaces a means is to hand of obtain- 

 ing species soon ripe and needing little heat. Of 

 all the seeds which had remained for four months 

 in the ice-case, only a few were found capable of 

 development when brought into a warmer tempera- 

 ture of 16° C. 



Maianthemum rifolium, D. C. (Smilacina 

 bifolia, Dest'.). — Will you give an old reader of 

 Science-Gossip room in your pages to state his 

 claim to the discovery of Maianthemum in the only 

 locality where it is really indigenous ? I have no 

 doubt the account will be interestingto your readers ; 

 but my chief reason for giving it is that the true 

 history of the plant seems but little known, so little 

 indeed that at a late meeting of the Leeds Natu- 

 ralists' Society a paper was read in which it was 

 stated that Mr. W. C. Backhouse, of York, was the 

 discoverer. Of this I was informed by one of the 

 presidents who knew my connection with the plant. 

 The history of its discovery is as follows : — In June, 

 1SG0, 1, accompanied by a friend, Mr. P. Reynolds 

 (then living at Ayton, near Scarborough), a field 



