28 



Our Native Ferns. 



CHAPTER III. 



FRUCTIFICATION IN FERNS. 



" But on St. John's mysterious night, 



Sacred to many a wizard spell, 

 The hour when first to human sight 



Confest, the mystic fern^seed fell." 



30. Spores and Sporangia. 

 — In the flowering plants (Pha- 

 nerogamia) there is a true sex- 

 ual reproduction, the ovules in 

 the female organs (pistils) being 

 fertilized by the pollen pro- 



Kig. 1. IDnlarged section through a sorus , , 



of Polypodium faXcatum, Kellogg, showing duced by the Stamens, thus grv- 

 the stalked sporangia. (Original.) ' ing rise to the embryo of the new 



plant. The Cryptogam i a on the contrary produce no flowers. 

 Instead of seeds developed from fertilized ovuJes,minute spores are 

 produced asexually from which new ferns are developed by a pecu- 

 liar process of germination very unlike that of flowering plants. 

 These spores are collected in little sacs known as sporangia or 

 capsules. The sporangia in the true ferns (Polypodiace^) are 

 collected in little clusters on the back of the frond or are variously 

 arranged in lines along the veins or around the margins. (Fig. i). 

 These clusters of sporangia are called sori, and 

 may be naked, as in Polypodium, or provided with 

 a special covering known as the indusium or in- 

 volucre, as in Aspidium (Fig. 10). The various 

 forms of the sori and indusia serve as the basis 

 for classification into genera and tribes, while each 

 sub-order has its peculiar form of sporangia. 



31. In the PoLYPODiACE^ the sporangia are 

 more or less completely surrounded with a joint- 

 ed vertical ring and at maturity burst open trans-' 

 versely and discharge their copious spores (Fig. 

 2). The clusters of sporangia may be marginal. 

 Fig. 2. Sporangium intramarginal or dorsal, according as they have 

 of Poll/podium md- f j^gj^ position at the margin or more or less re- 

 fr'pots.''''M'rifen^mote from it. They may be roundish, oblong or 

 Urged. (Original.) linear in shape, or arranged in variously forking 



