33« 



VA SCULA R CRYPTOGAMS. 



macrospores and microspores in the Lycopodiacese and Rhizocarpe:^ is manifested 

 only after the division into four of the mother-cells, which were previously alike 

 in the case of both kinds of spores. 



Vascular Cryptogams form a group connected with one another by very 

 obvious bonds of relationship, but may be divided into five parallel and diverging 

 series or classes. In the formation of a prothallium the Ferns and Equisetacese 

 show a marked affinity with the lowest stages of development of the Muscinese. 

 The Rhizocarpeae and Lycopodiaceae diverge in this respect greatly from these 

 classes, and in their mode of sexual reproduction form a transition to Phane- 

 rogams, — from Spore-plants to Seed-plants, as will be shown when treating of the 

 general characteristics of the latter. 



The proof that what is termed the Moss-fruit, i. e. the sporogonium, is, from its 

 position in the alternation of generations, the equivalent of the entire leafy and rooting 

 spore-producing plant of Vascular Cryptogams, was brought forward by Hofmeister 

 as long ago as 1851 (Vergleichende Untersuchungen, p. 139^). In connexion with the 

 relationships pointed out by him between the Lycopodiaceae and Coniferae, this discovery 

 is one of the most fertile in results that has ever been made in the domain of mor- 

 phology and classification. The researches of Pringsheim and Hanstein on the develop- 

 ment of Rhizocarps, carried out with great acuteness and deep penetration, those of 

 Nageli and Leitgeb on the roots of Vascular Cryptogams, and of Cramer on the apical 

 growth of the stem of Equisetacese and Lycopodiaceae (with which the more recent 

 labours of Rees made under Nageli's superintendence agree), have not only contributed 

 to a more accurate knowledge of this group of plants, but have especially cleared up the 

 fundamental morphological facts. Since the appearance of the first edition of this book, 

 our knowledge of the alternation of generations has been enriched by Millardet's 

 discovery of the male prothallium in Selaginella ; and the labours of Millardet, Stras- 

 burger, and Kny have resulted in a more complete acquaintance with the development 

 of the sexual organs and of the process of fertilisation itself in its details. 



The following systematic review will serve as a preliminary introduction to the group 

 of Vascular Cryptogams : — 



The sexual generation is developed from the spore, and is a thalloid structure of 

 small size; the archegonia have their ventral part imbedded in this prothallium; the 

 antherozoids are spirally-coiled threads, generally furnished with a number of cilia at 

 their anterior pointed end. The asexual generation, resulting from the fertilisation of 

 the oosphere in the archegonium, produces the spores, and is difterentiated into stem, 

 leaves, and roots. The branching of the stem is not axillary ; its tissue is differentiated 

 into epidermis, fundamental tissue, and closed fibro-vascular bundles; the sporangia are 

 products of the leaves ; the mother-cells of the spores arise from a central cell or from 

 a mass of sporangial tissue, and form the spores by division into fours after previously 

 showing a tendency towards bipartition. 



I. Isosporous Vascular Cryptogams. 



Only one kind of spore is produced ; the prothallium vegetates for a considerable 

 time independently of the spore, and produces antheridia and archegonia. 



^ [On the Germination, Development, and Fructification of the Higher Cryptogamia, and on 

 the Fructification of the Coniferae, by W. Hofmeister; translated by F. Currey; Ray Soc. 1862, 

 V- 434-] 



