BOTANICAL SUBJECTS. 



217 



recalls nothing so readily as a contracted and modified fern-pinna, 

 with its indusia, such as we see in Blechnum borecde. 

 Fig. 71. 



Fig. 71. Son of Blechnum boreale (" Hooker's Brit. Ferns," pi. 40). 



The anthers of the Scotch fir do so much more completely, 

 as wiU be seen by Fig. 72. They are exactly like a contracted 

 frond, with two dorsal sori, each sorus haying a double indusium. 

 Then each contracted frond of this fir, for the purpose of 

 protecting its pollen while unripe, is oyerlapped by the one below 

 it, so as to form an imbricate cone. 



Fig. 72. Anther of Scotch Fir, 



"We haye here pollen and spores as homologues, with the 

 difference that the former are naked, and emerge directly out of 

 the surfaxie of the stamina! blade, while the latter are enclosed in 

 the gland-like tip of a hair, the sporangium* 



* The spore is nothing but a bud, like any other bud. After it germinates 

 it produces a prothallus, or rudimentary flower, with sexual elements, as any 

 other bud does. The former evolves the flower at once, the latter takes time 

 to do 60. 



