PLATE XXIII.— MALE SHIELD FERN— <»«//«//«/. 



Fig. 1. Development of Spores. 



In each Sporangium a single central cell gives rise to sixteen mother-cells by successive division into 2, 4, 8, 

 and 16. 



Each mother-cell divides into four Spores, as shown. The cell-wall of each spore is differentiated into an 

 inner and outer coat, as seen in Fig. 2, and chlorophyll is developed in the contents. 



Fig. 2. Spore germinating. 



With moisture the Spore swells, and the outer, firm Exosporium ruptures, while the inner, delicate Endosporium 

 protrudes. As this grows a transverse septum is formed, and about the same time the lower cell gives forth the first 

 rootlet 



Fig. 3. Prothallium. 



The germinating Spore first produces a row of cells, then, by oblique division, a surface of cells, and finally the 

 flat expansion of the Prothallium. 



Male and female reproductive organs next arise on the under surface of the Prothallus. 



Antheridia, or male organs, arise among the bases of the root-hairs, and Archegonia, or female organs, near to the 

 notch. 



Fig. 4. Antheridium. 



The Antheridia are rounded projections, the contents of which break up into mother-cells, in each of which an 

 Antherozoid is developed. 



Fig. 5. The coiled-up Antherozoid is seen in the mother-cell. 



Fig. 6. Antherozoid free. 



Fig. 7. Archegonium. 



The central or germ cell is the point which the Antherozoids must reach in order to produce fertilizatioa For 

 this purpose there is a central canal open at the top, and bounded by four longitudinal rows of cells. • 



Life History Diagram. — The conspicuous Fern (1) developes Spores or Gonidia (2) on its under surface ; and one of these germinating 

 produces a Prothallium (3), afterVards producing male and female organs — Antheridia and Archegonia (4) — on its under surface ; 

 the central cell of the Archegonium becomes fertilized by the access of Antherozoids, and the Fertilized Germ-cell (5) developes 

 into the Fern(i). 



CLASSIFICATION. 



Sub-kingdom. — Vascular Cryptogams. 

 True Roots. 

 Fibro-vascular bundles. 



Prothallus bearing reproductive organs comparatively inconspicuous. 

 Class. — Filicinae. 



Stem usually unbranched. 

 Leaves large and compound. 



Sporangia in clusters, and each sporangium developed from a single epidermal cell. 

 Spores of one or two kinds. 

 Order. — Filices. 



Leaves without stipules. 

 Spores of one kind. 



Prothallus independent and monoecious. 

 Genus. — Aspidium. 



