57*^ EXPER,IMENTS IN TEACHING BOTANY. 



mustn't say so to the examiner."' So they go, and with girHsh 

 gaiety and irresponsibiHty tell the examiners that they applied 

 gloriofuselin and proved that wood was wood. Moreover, as 

 one of my pupils shrewdly remarked, if we have to believe the 

 chemists, why not at once believe the botanists and have done 

 with it? 



The iodine test for starch is on a widely different footing, 

 Iodine is a familiar household substance : the pupils know its 

 colour and its smell : they know how it stains their fingers and 

 their handkerchiefs. They can watch its gradual efliect on the 

 canna or potato starch, whose form and structure are well known 

 to them. They can then see its efifect on, say, Euphorbia 

 granules, and are able to bring these dumb-bell shapes into the 

 same category with the ellipsoids. The iodine test enlarges their 

 knowledge : the phloroglucin doesn't. 



Some of the text-book experiments are logically invalid. 

 We are. for instance, told to find the upward passage of water 

 by putting a cut shoot in a coloured solution. But will a cut 

 shoot behave in the same way as the integral plant? I know a 

 teacher who cut a pumpkin shoot, put it in eosin, and told her 

 pupils to make deductions. They found the sieve-plates so beauti- 

 fully stained that they concluded that water passes up the sieve- 

 tubes. Their deduction ,was quite right ; it is the experiment 

 that v.as wrong. Capillarity had interfered, and the interference 

 would always be visible if sieve-tubes were always as large as 

 those of the gourds. I suppose the only logical way of doing 

 that experiment would be to grow a plant by water-culture, and 

 then some day colour the liquid. 



Again, some experiments are utterly unnecessary. Any one 

 who has examined the structure of the epidermis must see that 

 the stomas are the only inlets and outlets for air and water 

 vapour. Why then torture leaves with vaseline or dip them in 

 hot water? A recent question was "Devise an experiment to 

 show that transpiration is effected only through the stomas." You 

 tnay as well say, " Devise an experiment to show that the inmates 

 of a house can go in and out only by the doors and windows, 

 and exceptionallv by the chimneys." 



After all, whv discourage the use of the microscope? There 

 IS nothing like it for revealing the relation of structure to func- 

 tion, which is the main secret of complex life. The only draw- 

 back, a distorted sense of proportion, is easily counteracted by 

 progressive use of the naked eye. magnifving glass, low power 

 and high power: and also bv showing familiar objects under the 

 plass. It is a highly-efifective extension of that most desirable 

 thing, direct observation, and is no more to be deprecated than 

 the use of spectacles by the near-sighted. 



A chief reason for the ban on the microscope seems to be the 

 time lost for a large class. Further, there is the trouble of 

 making the slides. Bought sections, like the dried plants of the 

 herbarium, are only an accessorv: the sections should be cut, if 

 not by the pupils themselves, at least in their presence, and from 



