CORRESPONDENCE. 107 



Geology. — A interesting deposit of shell-marl, overlaid by peat and 

 a considerable thickness of fine clajs has been exposed in excavations 

 near Leicester. I hope to give particulars in the "Midland Naturalist" 

 at an early date. A minute examination of the interesting series of 

 freshwater shells in the marl and lower part of the peat is now being 

 naade. The peat also contains numerous insect remains, whilst the marl 

 is so full of the seeds and stem incrustations of Chara as to suggest the 

 probability of its having been formed in great part by this plant. — H. 



The Meaning of Knowledge. — Mr. Watson thinks I have unduly 

 limited the meaning of this word ; but I have nowhere asserted that it 

 bore no other meaning than the one I assigned to it. Like a large number 

 of EngUsh words, it has several shades of meaning, most of which are 

 included in my definition. I wished only to point out the incorrectness 

 of its use as a sjTaonj-m ol belief, the difference between knowledge and 

 belief being very wide, and the common confusion between them a 

 Bource of grave and constant error. — F. T. Mott. 



Postal Miceoscopical Society. — Allow me to draw the attention of 

 your microscopical readers to this society, established about four years 

 ago, for the purpose of encouraging the study of such subjects as are best 

 elucidated by the microscope, by sending boxes containing from twelve to 

 sixteen objects that are expected to be mounted by the sender, with an 

 explanation of each. For that purpose a small book accompanies each 

 box in which members wi'ite their remarks, explanatory or critical, on the 

 different slides. The present president, Mr. Tuffen West, and Messrs. 

 Underbill, Hammond, Kyngdon, and others, frequently illustrate the 

 objects by excellent coloured sketches ; the notes and drawings are 

 in themselves very interesting. The subscription of 2s. 6d., (exclusive of 

 postage, &c.,) and'2s. 6d. admission fee, are the only expenses, except four 

 ehdes a year from each member to help to fill up the boxes in his circuit. 

 Mr. A. Allen, of 1, Cambridge Place, Bath, the secretary, will, I am sure, 

 be pleased to give every information to enquirers. Cannot our Bir- 

 mingham friends form a section from among so many excellent micro- 

 Boopists? — Thomas Partridge, M.P.M.S., Stroud. 



Botanical Queeby. — Will you or some of the botanical readers of 

 our Journal oblige by informing me of what use are the " thickened 

 hollow spots" (of Bentham) at the base of the petals of the genus 

 Ranunculus, and whether they occur in any other genera or species ? — 

 H. F. Devis, King's Heath. 



[These " hollow spots " are what are known as nectaries. Their 

 function is that of secreting the nectar or honey, and they often serve an 

 important purpose in the economy of flowering plants, helping to bring 

 about cross fertilisation ; thus, the nectar they secrete is much sought 

 after by many insects, and in obtaining the honey the insect frequently 

 gets dusted with, the poUen from the ripe anthers of the flower visited. 

 This it carries away, and in visiting another flower in search of more 

 honey, deposits the pollen carried from flower No. 1 on the stigma of 

 flower No. 2. In this way it unconsciously aids in bringing about the 

 fertilisation of the ovules. These nectaries vary in form, colour, &o. ; 

 in Cruciferae they occur as little gi-een warts at the base of the filaments, 

 in Umbelliferae they form the fleshy disk at the base of the styles ; 

 Bometimes they occur as spurs at the base of anthers, as in the violets ; 

 again as spurs at the base of the petals, as in many orchids and in the 

 larkspur. They occur as pores at the base of the petals in another of 

 om- British plants, Fritillaria Meleagris. For full information see 

 Balfour's "Manual" or Sach's " Text-book of Botany," under the head 

 Nectaries. — J. E. B.] 



