USE OF THE MICROSCOPE IN BOTANY. 2$ 



about 200 diameters, and you will notice some very 

 pretty groups of octahedral or prismatic crystals. 

 They are generally composed of oxalate of lime, or 

 of carbonate, sulphate, and phosphate of lime. Dr. 

 Carpenter says that "certain plants of the cactus 

 tribe, when aged, have their tissue so loaded with 

 raphides as to become quite brittle, so that when some 

 large specimens of C. senilis, said to be a thousand 

 years old, were sent to the Kew Gardens from South 

 America, some years since, it was found necessary for 

 their preservation during transport to pack them in 

 cottcn like jewellery."* What office these crystalline 

 bodies fulfil, or whether they fulfil any at all, is not 

 known. Raphides have been artificially produced 

 within the cells of rice-paper. Mr. Quekett filled the 

 cells with lime-water by means of an air-pump, and 

 placed the paper in weak solutions of oxalic and phos- 

 phoric acids. " The artificial raphides of phosphate 

 of lime were rhombohedral ; while those of oxalate 

 of lime were stellate, exactly resembling the natural 

 raphides of the rhubarb." 



The spiral vessels of plants will amply repay you for 

 investigation by their extreme beauty : they are easily 

 seen by macerating the stems or leaves in water, or 

 by boiling them. These spiral vessels are cylindrical 

 tubes with cone-like ends, within which fibres wind in 

 a corkscrew fashion. In some cases the tube contains 

 only one spiral fibre ; in others as many as twenty 

 have been counted (Fig. 5). These vessels are found 

 in all parts of plants excepting the roots. They a-e 

 very beautiful in the seeds of certain plants, as in the 

 strawberry and hazel-nut. Every one is familiar with 

 the brown coating that surrounds the common nut ; 

 scrape a portion of this membrane off the kernel, and 



* " The Microscope," p. 400. 



