VOL. LX— NO. I 



HAMILTON, ILL., JANUARY, 1920 



MONTHLY, $1.00 A YFAR 



PHYSIOLOGY OF NECTAR SECRETION 



By Dr. Wm. Trelease, Botanist, University of Illinois. 



WHAT we call individual plants 

 are complex communities of 

 real but microscopic individ- 

 uals, which biologists call cells. 

 These are associated in numerous 

 sub-communities, differing from one 

 another in structure and function. 

 Their specialization results in a di- 

 vision of labor and a corresponding- 

 ly large total efficiency, much as spe- 

 cialization and division of labor lead 

 to efficiency and productive possibili- 

 ties in a nation consisting of States 

 and these of smaller communities 

 made up of trades, guilds and profes- 

 sions, which in co-operation follow the 

 manifold activities that characterize 

 a nation and collectively constitute 

 the national life of its individuals, 

 which is far more effective and 

 greater than the individual life of 

 any one person or class. 



The active, living part of a cell is 

 its protoplasm— the physical basis of 

 life, as Huxley calls it — in animals 

 and plants alike. Commonly this 

 protoplasm encloses itself by a wall 

 of cellulose, an organic substance 

 manufactured by the protoplasm. 

 Where two cells are in contact, they 

 are usually flattened against one-an- 

 other. When men first began to use 

 the microscope, only a little over two 

 centuries ago, it was the walls and 

 shapes of cells that attracted atten- 

 tion, and the resemblance to honey- 

 comb on a small scale was so strik- 

 ing that the cavities were naturally 

 called cells. 



Protoplasm itself is a very com- 

 plex substance chemically, and even 

 the much simpler cell-wall is far 

 from being always of really one 

 identical substance. A considerable 

 part of the thickening of matured 

 cell-walls has been laid down on the 

 original partition between two cells, 

 and not only differs from this but is 

 not alike in different kinds of cells, 

 and in structures like wood and cork 

 it is impregnated with other materi- 

 als that affect the cell wall very 



greatly in such respects as hardness 

 and permeability to water. 



The shells of nuts, for instance, 

 are so impervious that they are com- 

 monly "stratified" by planters, so 

 that their hard shells may disinte- 

 grate more or less as a preliminary 

 to germination; a process that not 

 infrequently requires more than a 

 year unless hastened by some expedi- 

 ent like that of passing haw fruits 

 through the digestive mill of poultry 

 as a means of softening their bony 

 cores, or filing the hard envelope, 



Part of flower of Geranium pyrenaicum. N. 

 nectaries; et. stamens. Greatly magnified. 

 Copied from Bonnier's "Les Nectaires. 



which is a favorite trick of garden- 

 ers with the nut-like fruits of the 

 lotus or with canna seeds. (This 

 is similar to the scarifying of sweet 

 clover seed. — lEditor). This is the 

 reason that several times as much 

 clover seed — even good seed — must 

 be used on an acre as seems neces- 

 sary for securing the desired number 

 of plants. One of these modifications 

 is usual in the outer layers of cell 

 walls on the surface, and it is called 

 cuticularization. Cuticularized walls 

 are more or less completely water- 

 proofed. When the cells that pro- 

 duce nectar are at the surface, their 

 outer walls are cuticulariztd in this 

 way: when they are within the nec- 

 tary and the nectar passes out 

 through stomata, this is scarcely, if at 

 all the case. 



The greater part of nectar is water 

 which reaches the surface from 

 within the plant cells. To do this it 

 must pass through walls that are lit- 

 tle if at all cuticularized, or it must 

 break through the cuticle. This does 

 not mean that it must break through 

 the entire cell wall; a small part of 

 this is modified by the protoplasm 

 into a gum or mucilage or some sim- 

 ilar substance, and the water accum- 

 ulates in this layer and swells it un- 

 til the overlaying cuticle is burst. 

 Some form of sugar is a frequent re- 

 sult of this disintegration of cellu- 

 lose. Dissolved sugars pass through 

 the ordinary celulose wall, but they 

 do not pass through the ordinary 

 surface layer of protoplasm in the 

 outer cells. 



When water is separated from a 

 solution like that of sugar by a fil- 

 ter of this sort, which allows wajer 

 to pass, but is not permeable to the 

 dissolved substance, the action is set 

 up that physicists call osmosis, and 

 water accumulates on the sides of the 

 dissolved substance until it exercises 

 a very considerable pressure. This 

 osmotic action not only bursts the 

 cuticle, when it starts beneath it, 



