MICROSCOPIC OBJECTS. 24 



Fig. 47. Testa of Seed of Collomia (Collomia grandiflora), 



x50. 



The spiral fibres in the cells of the testa of this seed form 

 a good object in which to observe the extreme elasticity of 

 spiral fibre. The best way to show it is to cut a very small 

 and thin slice from the outside of the seed, to place it on a 

 glass slip, and then add a drop of alcohol to it, and cover 

 with thin glass, next adding water in sufficient quantity to 

 fill up the space left between the glasses. If the object is 

 now viewed under an inch or J-inch object-glass, the uncoil- 

 ing of the spiral fibres will be beautifully seen. 



It may be mounted in weak alcohol and water about 

 alcohol 1 part, to water 6 parts. 



Fig. 48. Testa of Vegetable- Ivory Nut (Phytelephas macro- 

 carpa), x 120. 



The structure of the testa of the Vegetable-Ivory nut is not 

 unlike that of the nut itself (see fig. 18), the peculiar rayed 

 appearance being also caused by the formation of the secondary 

 deposit. This kind of tissue is often called sclerogen. The 

 drawing might be mistaken for that of the petal of the 

 Geranium, which it greatly resembles ; but upon closer exa- 

 mination the cell-wall will be seen to possess a different 

 character (see fig. 37). The husk, or, as it is called, the testa, 

 of this nut is of a brownish colour ; it may be prepared by 

 grinding down to an extreme thinness, and then mounting in 

 Canada balsam in the usual manner. 



