24 THE AMERICAN' BOTANIST 



this is undLi'stood, a seed containing an embryo and endosperm 

 may be attempted. Only after all the parts of this second seed 

 have been made out should the pupil be given seeds that lack 

 plumules or those in which the endosperm is peculiarly located. 

 Last of all should come the monocot seed. The seed usually 

 studied is that of the corn, but large as this is, the embryo 

 forms so small a part of it, that a seed with a larger embiyo is 

 much to be desired. It is unfortunate that many large mono- 

 cot seeds have such small embryos. If anybody know^s of a 

 monocot seed with parts more easily made out than those of 

 the corn are, it would be a great aid, to teaching if he would 

 make it known. 



The Selection of a Lens. — In selecting a simple lens 

 or magnifying glass, many people are puzzled when they come 

 to com])are prices and magnifying powers. An instrument 

 may l)e bought for fifteen cents that will magnify as much as 

 one tiiat costs half as many dollars and the beginner naturally 

 inquires where the difference comes in. In answer it may be 

 said tliat there are two differences, one in the lens, the other 

 in the setting. The cheapest lenses, and also the most ser\dce- 

 able considering the price, are certain French glasses mounted. 

 in a nickel case and costing fifteen and tv,enty-five cents. 

 Equally handy are the socalled "thread testers" wliich may be 

 purchased (jf jewelers and stationers for twenty-five to fifty 

 cents. These fold up and may be carried in a small pocket or 

 even a pocket-book. Still otlier glasses may be had mounted 

 in rubber cases with one. t\vo or three lenses. All these in- 

 struments, IioweN'cr, have one decided drawback ; when the ob- 

 ject tu be viewed is brought into focus, it can l)e seen clearly 

 only in the center of the "Meld." To make the object show dis- 

 tinctly additional lenses must be used and this is the first thing 

 that increases the cost. One kind of magnifier designed to 

 overcome this defect is the coddington, in which a thick cylin- 

 drical piece of glass lens-shaped on the ends iias a ring cut 

 round the middle and painted black. This is mounted in a nick- 



