120 Botanical Microtechnique 



recommended here are available in most parts of the country or can 

 be grown in the greenhouse or even in a window box. The local 

 florist shop and commercial green houses are fruitful sources of mate- 

 rials, especially exotics. Algae, fungi, and br\ophytes can be found 

 in abundance when one has learned where to look. Such local foraging 

 and field trips afford a wealth of material. 



The sequence in which specific recommendations are arranged 

 in this manual takes cognizance of the customary arrangement of 

 topics in textbooks of botany. Laboratory courses in general botany, 

 anatomy, and histology are oriented around topics and fundamental 

 problems that cut across taxonomic lines. The leaf, for example, is 

 studied as a functional and structural unit, a food-making organ. A 

 comprehensive study of the leaf from this point of view necessitates 

 a comparison of leaves of a wide range of vascular plants and perhaps 

 even of mosses. The stem and root arc likewise studied as organs 

 having structural diversity and functional modifications but never- 

 theless having some fundamental pattern. In addition to that elusive 

 entity, the typical organ, it is essential to examine variations and 

 modifications of the basic pattern. A comprehensive study of vascular 

 anatomy thus embraces vascular plants from Lycopodium to Orchis. 



From the standpoint of technique each organ presents its char- 

 acteristic problems. For example, broad leaves of plants in widely 

 separated taxonomic groups have in common such problems as col- 

 lecting, subdivision in sampling, and orientation in sectioning. If we 

 were to consider in its entirety some one species, like an oak, we would 

 find that its root tips, embryo sac, and old stem [jresent very different 

 problems of technique. 



These considerations have led to the arrangement of Part II, in 

 which categories of organs as well as taxonomic position are used as 

 majoi- cha])ter topics. 



