THIRD GROUP. 



THE VASCULAR CRYPTOGAMS. 



UNDER this name 1 are included the Ferns (in the narrower sense including Sal- 

 viniaceae and Marsileaceae), Ophioglosseae and Marattiaceae, Equisetaceae (in the 

 wider sense of the term), Lycopodiaceae, Psilotaceae, Selaginelleae and Isoeteae. In 

 this group as in the Muscineae the process of development divides into two generations 

 which are very distinctly separated morphologically and physiologically ; first of all the 

 spore gives rise to a sexual generation ; from the oosporeof its archegonium proceeds 

 a new plant, an asexual generation which forms no sexual organs, but numerous 

 sporangia. In the true Ferns and Equisetaceae the spores are all alike ; the Sal- 

 viniaceae and Marsileaceae (Rhizocarpae) subdivisions of the Ferns, the Selaginelleae 

 also and the Isoeteae, have two kinds of spores, large and small, macrospores and 

 microspores. 



The First or SEXUAL GENERATION (oophore, oophyte), produced from the 

 spore, is never anything but a thallus ; it never reaches, as in the more highly developed 

 Mosses, to the stage of a differentiation into stem and leaf, but continues small and 

 delicate, and its life comes to an end when the development of the second genera- 

 tion begins, unless it happens to be rendered perennial by adventitious shoots, as in 

 Gymnogramme leptophylla ; to outward appearance, therefore, it is merely a forerunner 

 of the after-development of the plant, a kind of transition from the germinating spore 

 to the variously differentiated second generation ; hence the name prothallium for this 

 first generation in the Vascular Cryptogams, the generation which produces sexual 

 organs. 



In the true Ferns, Equisetaceae and others, the prothallium resembles the thallus 

 of the lowest Hepaticae ; these prothallia in some cases continue to grow for a 

 long time, contain an abundance of chlorophyll, and produce numerous rhizoids ; 

 thus they depend on themselves for their subsistence, and when arrived at sufficient 

 strength they produce antheridia and archegonia usually in large numbers. In the 

 Vascular Cryptogams, which have two kinds of spores and are therefore termed 

 Heterosporous Vascular Cryptogams, namely the subdivisions of Ferns above-mentioned, 

 and the Selaginelleae and Isoeteae, the separation of the sexes is previously indicated by 

 the two kinds of spores, for the macrospores are female, and develope a very small 



1 The Vascular Cryptogams are also known as Pteridophytes. 



