THE AMERICAN BOTANIST 119 



see much more of botany than is represented by the specimens 

 brought back. Most teachers, however, will find it easier to 

 have some place in which to grow their material. If the 

 school has a school garden, one should insist upon a part being 

 devoted to the growing of plants with tendrils, thorns, clado- 

 phylls, and other structures that are needed. Often, however, 

 the teacher will be obliged to grow such things in his home 

 grounds and get his reward entirely from the consciousness 

 that his subject has been properly taught. 



Growing Mucor. — Everybody who takes up the study 

 of fungi becomes acquainted with the black mold {Mucor) 

 which appears on bread and other food products, but possibly 

 because it is so abundant and ubiquitous little attention is paid 

 to special methods of cultivating it. One of the best schemes 

 we have seen for getting specimens that the dullest pupil can- 

 not fail to see well was originated by Mr. F. A. Houghton. 

 By his method a drop of clear gelatin is placed on a glass slide, 

 some mold spores sown in it and then placed in a moist chamber 

 for growth. In a short time the mycelia may be seen pushing 

 into various parts of the food material, and the young sporo- 

 phores rising from it. If the specimens are properly cared for 

 they may be examined several days in succession and will give 

 the pupil a better idea of the habits of this mould than any 

 series of prepared slides or living material taken from bread 

 or other moldy objects. 



Growth Rate of the Giant Cactus. — Some investi- 

 gations recently made concerning the rate of growth of the 

 giant cactus {Cereus giganteiis) have resulted in some rather 

 astonishing information. Cacti of all kinds are known to be 

 rather deliberate in adding to their bulk and this species is no 

 exception. Specimens less than five inches high are known 

 to be ten years old while the fairly large specimens, running up 

 to fifteen feet or more in height, require at least sixty years to 

 attain this size. 



