88 The Microscope. 



fronds. These vessels are exceedingly small smaller, 

 indeed,, than the seeds of most plants and they are 

 arranged in a great variety of ways in the different 

 kinds of fern ; but in nearly all ferns they are globular, 

 contain a number of extremely minute spores, and 

 grow from the back of the frond on a curiously -jointed 

 stalk, and this stalk runs up one side of the theca, and 

 bends round it like a ring. 



This ring is elastic, and so long as the spores are 

 unripe, and the theca soft and green, it maintains 

 its bent shape, and acts as a band. But when the 

 theca becomes stiff, and the spores ripe, the elastic 

 ring suddenly straightens itself with a great jerk, 

 tears the theca open, and scatters the tiny spores in 

 all directions ! Plate VII., fig. 1, represents one of 

 the thecae of a fern, called the Black Maidenhair 

 Spleenwort ; and fig. 2 a similar theca with the ring 

 in the act of straightening itself. 



I have often brought a number of fern-fronds into 

 the house to examine while fresh with the microscope ; 

 and as the heat of the room hastened their drying, the 

 rings soon began to straighten themselves, the thecas 

 to tear, and the spores to scatter about. I have 

 shown this to friends, and been asked, " What are 

 those live things ?" 



Fig. 3 shows part of the frond, of the size of the 

 original ; the slit-like marks are the groups of theca3. 

 In fig. 4 one of these groups of thecas and part of 

 another are shown magnified twelve diameters. From 

 this an idea may be gained of the animation of the 

 scene. 



