5 8 PLANT PHYSIOLOGY 



SECTION 1. THE PHYSICAL STRUCTURE AND 

 PROPERTIES OF PROTOPLASM. 



A knowledge of this subject requires, first of all, an exact 

 observational study of living Protoplasm from favorable plant 

 sources. Thus is presented a definite inquiry as follows: 



What physical structure and properties, as manifest in opti- 

 cal qualities, in texture, in density, in motility, and in differen- 

 tiations of substance, are visible to exact observation under favor- 

 able conditions in the living Protoplasm of plant cells? 



Since Protoplasm exists in most plants only in minute and thinly 

 distributed masses, it is necessary to resort to the aid of the microscope. 



OBSERVATION. Select the best of the available materials showing 

 living Protoplasm; mount each in tap-water on a slide under a cover- 

 glass; examine carefully with a microscope, first with lower powers, 

 and then with the highest at command. The results of the study 

 should be expressed in such a combination of drawing and words as 

 will most accurately and vividly bring the facts before the mind of a 

 reader. 



MATERIALS. The best, because most clearly visible, material occurs 

 in transparent-walled, thread-like, or hair-like structures. First among 

 these are the hairs on the stamens of the Tradescantia virginiana, or Vir- 

 ginica (Spiderwort), in any of its several varieties, of which var. pilosa of 

 gardens is very good. The hairs should be taken, grasped with fine forceps 

 by their bases, from just opening or even still unopened blossoms. This 

 plant ordinarily blooms in gardens in May and June, but may readily be 

 obtained in perfect condition from September to December by planting in 

 a cold frame or greenhouse and cutting it back near to the ground just be- 

 fore it blossoms in spring. Other species of Tradescantia, especially T. ze- 

 britia (Wandering Jew), commonly grown in greenhouses, yield hairs nearly 

 as good. A fair substitute is offered by the hairs on the stems and leaves 

 of young Squash plants, which may be grown at any time in pots from seed, 

 requiring only two weeks for sufficient development, while ether Cucurbi- 

 tac&t also afford good hairs. Other plant hairs, such as those from Cypri- 

 pedium spectablle (Lady's Slipper), are also available. Many root-hairs, 

 grown in germinators, the mycelia of some Fungi, and transparent-walled 

 pollen-grains, especially if they form tubes, or even burst in the water, are 

 also excellent. Of great value are the Stoneworts, species of Chara and 

 Nitella, especially the latter; these are found nearly everywhere in ponds 

 and slow streams. If brought into a greenhouse, allowed to root in a layer 

 of mud at the bottom of a tub, and kept in a moderately lighted place, they 

 will continue to form the young tips, which are best for this purpose, during 



