4 INTRODUCTION 



finer details of protoplasm and its derivatives. For general morpho- 

 logical work, sections are not cut so thin. About 10 /x is a serviceable 

 thickness, with 5 /x for oil immersion details. Algae and fungi, with 

 their small nuclei, usually need 3 or 2 /x sections. With improvements 

 in microtomes and in technique, the 1 ^ section is not so rare, and rib- 

 bons of root-tips have been cut at | /x. A microscope, giving several 

 times the magnification of any microscope now on the market, is in 

 an advanced experimental stage. Should such microscopes get into 

 use, it would be necessary to regard a 2 /x section as rather thick, and 

 nothing thicker than 1 ^ could be regarded as thin. Such a micro- 

 scope would bring great improvements in technique. 



Every investigator whose work demands a microscope should study 

 technique until he gains such a grasp of fundamentals that he will be 

 able to make the modifications which individual problems may re- 

 quire. Those who think that such work is mere mechanical drudgery, 

 which can be done by an assistant, are likely to become armchair in- 

 vestigators, drawing false conclusions or becoming scholastic grafters, 

 according as the assistant is mediocre or talented. Besides, there is 

 always the danger that a talented assistant may "hold out" some- 

 thing. A younger member of a faculty, doing research work for his 

 superior, may make an important discovery but, knowing that his 

 superior has little knowledge of the progress of the investigation, 

 may "hold it out" and, later, pubhsh it himself, preaching the same 

 sermon from a different text. Benjamin Franklin's advice, "If you 

 want your business done, go; if not, send," applies very well to investi- 

 gations involving histological technique. 



We strongly advise the student to collect his own material in the 

 field, for such collecting is a valuable part of a botanical education. 

 There are details of habitat and behavior which are never described 

 in books. One learns gradually, by experience, that certain kinds of 

 plants grow in certain kinds of places; and further, that not only the 

 season, but even the weather, may be an important factor. A heavy 

 rain may cause some algae to disappear; while the same rain, followed 

 by a few days of sunshine, will bring ideal conditions for collecting 

 Myxomycetes and many other fungi. One learns that while Lycogala 

 is pink, it is in the free nuclear condition, and that Stemonitis is in 

 that condition as long as it is white; and Volvox may be abundant at 

 the bottom of a pond when there is scarcely any in suspension. The 

 successful investigator learns how a flower bud should look, if it is to 



