22 



March 6th, 1873. 



Crystal Prisms. — These are prismatic plant-crystals, quite dif- 

 ferent from though often confounded with raphides. Mr. FuUagar 

 exhibited specimens of the prisms in the bulb-scale of the onion, in 

 order to show how a very beautiful misroscopic object is always at 

 hand, and Colonel Horsley showed further that its beauty was much 

 increased by polarised light. The crystals occur singly, very vari- 

 able in size, lying across the tissue-cells, and in pretty crosses, 

 soldered together at intersecting parts. According to Mr. Gulliver 

 (' Annals of Nat. Hist.,' April, 1864) these prisms occur regularly 

 in the bulb-scales of Allium ascalonicum, A. Cepa, A. Porrum, and 

 A. sativum, but not in A. schcenoprasum, A. angulosum, A Moly, 

 A. mayicum, and A. ursinum. Crystal prisms, not in crosses, may 

 be well examined at any time in such officinal things as guaiacum 

 bark, quillaja, and the sweet-scented orris, and sometimes in 

 company with raphides, in various fresh Iridacae, such as Iris ger- 

 manica, a very common plant in cottage gardens. Measurements 

 and other details are given in the ' Popular Science Review,' vol. 

 4, p. 578. 



Paramecium feeding on Desmids. — To show how freely Para- 

 mecium feeds at this season, Mr. Fullagar brought specimens from 

 his aquarium, which were seen greedily injesting three species of 

 Closterium. 



April 3rd, 1873. 



Raphides, Sphcer aphides, and Crystal Prisms. — Slides, draw- 

 ings, and extemporaneous preparations of these beautiful plant- 

 crystals were exhibited and explained by Mr. Gulliver, who read 

 a paper thereon, and remarked that, considering their interest 

 both as microscopic objects and botanical characters, it is sur- 

 prising that they have not received more attention. They are 

 ignored in our Floras, and but crudely described in our treatises on 

 the microscope. Hence, these crystals require more explicit treat- 

 ment, so that experts may realise their value as taxonomic charac- 

 ters, and ladies and novices find an additional source of microscopic 

 amusement and instruction for idle time, thus not idly spent. Our 

 present knowledge of the value of raphides as natural characters in 

 systematic botany is chiefly confined to the memoirs by the author, 

 published piecemeal in various journals, and summarised in the 

 'Popular Science Eeview ' up to October, 1865, since extended in 

 the ' Annals of Natural History ' of that year, and in several num- 

 bers of ' Seemann's Journal of Eotany,' and the ' Quarterly Journal 

 of Microscopical Science.' But independent inquirers have not yet 

 subjected those observations to such practical criticism as would 

 prove either their erroneousncss or truthfulness. "We hear only, 

 and but seldom, of exceptions, whether correct or incorrect, as it' 

 these were not well known to be common to some of the best 

 diagnostic characters in natural science. 



The chief source of error has been in the confusion of terms, for 



