MICROSCOPIC OBJECTS. 23 



Fig. 45. Seeds of the Least Toad-flax (Linaria minor), x 20. 



The testa of this seed is much furrowed; and there are 

 many seeds partaking of this character, of which the Poppies, 

 Toad-flaxes, &c. contain some of the best examples. Many 

 seeds have also a number of rayed protuberances rising from 

 their surface, as in the Campions, Catchflies, &c. The testa 

 may be separated from the seed and mounted as a transpa- 

 rent object ; or the seeds may be mounted in a dry opaque 

 cell. But it is best, if possible, to mount them in both ways, 

 as the real structure is then better seen. Many seeds, when 

 viewed opaquely, have a striking resemblance to the eggs of 

 Moths and Butterflies (see Insects' eggs) . 



Fig. 46. Seed of Eccremocarpus (Eccremocarpus scaber), 



x20. 



Winged seeds like the present always present a beautiful 

 structure under the low powers of the microscope. Some of 

 the best forms are Calosanthes Indica, Paulownia imperialis, 

 Lophospermum scandens, Pentstemon, &c. Seeds have two 

 skins or coats, called the testa and tegmen ; the former and 

 outer membrane (testa) is generally greatly thickened and 

 hardened by the formation of the secondary deposit, as in 

 fig. 48. Sometimes the surface is furrowed, as in fig. 45 ; 

 occasionally it is quite smooth ; and it is rarely covered with 

 spiral-fibrous cells, as in Collomia (fig. 47) . 



Eccremocarpus-seeds are best prepared by boiling in nitric 

 acid 1 part, water 2 parts, which quickly changes the colour 

 to a light brown, when the centre of the seed must be taken 

 out, and the skin well washed and mounted in balsam as usual 

 if wanted for the polariscope, or, if not, in fluid. 



