26 



THE AMERICAN BOTANIST 



this type. Some seeds have coats that exclude oxygen and 

 other gases and thus hinder the growth of the seedhng. For 

 a long time it has been known that certain seeds will not grow 

 while exposed to light and that others are equally sensitive to 

 darkness. These various delays in sprouting, though at first 

 glance apparently harmful to the species, are not always so. 

 If every seed grew the first season, it is quite possible that all 

 the plants might be destroyed. A few seeds held over to other 

 years gives the species several chances to survive. In such 

 species, the seeds give a distribution m time similar tO' the dis- 

 tribution in space usually resulting from the production of such 

 structures. 



Identifying Plants by Chemistry. — At last, species 

 making by fiat seems tO' be going out of fashion. It has been 

 discovered by E. T. Reichert of the University of Pennsyl- 

 vania that species and varieties of both plants and animals are 

 sharply distinguished from one another by the structure of 

 their molecules, and are thus easily identified by chemical 

 means. Starch in plants, for instance, is known to consist of 

 carbon, hydrogen and oxygen in six, ten and five parts, re- 

 spectively. This gives a large number of atoms which con- 

 ceivably may be arranged in a vast number of different posi- 

 tions and still have the chemical formula for starch. In ani- 

 mals, the haemoglobin or red coloring matter of the blood 

 may theoretically exist in more than a million different 

 forms and still be haemoglobin. When tested in various ways, 

 the haemoglobin from each species reacts differently, and by 

 means of these reactions, the student is able to recognize gen- 

 era, species and even varieties. The study of starch in plants 

 has given equally remarkable results. Each property of the 

 starch grain, whether it be manifested in peculiarities of form, 

 size, hilum, lamellation, fissuration, or reactions to chemical 

 reagents, appears to be a specific character, thus allowing of the 

 certain recognition of species; in fact, the author says, 'Tt 



