CRYPTOGAMIA. 409 



with the Mosses and their allies. These two groups are distin- 

 guished from each other by the structure of their tissues. The 

 Ferns and their allies possess a well-developed vascular system, 

 and under the name of Vascular Cryptogams are arranged the 

 Equisetacece, Filices, Lycopodiacece, Selaginellacece, and Rhizocarpece. 

 The Mosses and their allies the Hepaticce (forming the class called 

 the Muscinece) possess no true vascular system, though the tissues 

 in the stems of Mosses have the character of vascular bundles of 

 the most rudimentary kind. In neither Mosses nor Hepatics do 

 true roots, in a morphological sense, occur, though they possess 

 organs (root-hairs) which discharge similar functions. In spite of 

 these defects in structure, the Mosses must still be looked upon as 

 standing higher in the scale, from an anatomical point of view, 

 than such Phanerogams as the Lemnacece^ which have neither true 

 stem nor true root. 



Sexual and Asexual Stages. In their life-history Vascular 

 Cryptogams pass through two morphologically and physiologically 

 distinct generations a sexual and an asexual ; and this holds true 

 of all Cormophytal Cryptogams. The spore is borne in various 

 ways in different families ; in the familiar case of Ferns it is borne 

 in capsules or sporangia usually on the back of the frond. When 

 it germinates, it produces a thalloid layer of cells called the pro- 

 tliallium, and it is on this that the sexual organs are formed. The 

 prothallium contains much chlorophyll, and forms numerous root- 

 hairs. It is soon in a position to nourish itself, and by-and-by 

 produces the male (antheridia} and female organs (archegonia) 

 (see fig. 493). The antheridia give rise to spermatozoids, which 

 fertilize the archegonia. This is the sexual generation. 



Out of the archegonium springs the asexual, leaf-bearing gene- 

 ration, which, in common language, is usually called a Fern, a 

 Horsetail (Equisetuni), &c. It bears the spores, as described, and 

 these in their turn again produce the sexual generation (prothal- 

 lium), and thus the life-history proceeds in alternate sexual and 

 asexual generations. The asexual plants possess a true vascular 

 system, differing in details from that of Phanerogams ; and a more 

 special description of their structure will be found under the head- 

 ings to which they are referred. Their apical growth usually pro- 

 ceeds from a single terminal cell. A remarkable exception to the 

 rule of alternation of generations is found in the reproduction of 

 Pteris cretica. Mr. Farlow * discovered that no female organs are 

 formed on the prothallium of this Fern, though the male organs 

 attain full development and produce spermatozoids. The leaf- 

 bearing generation springs from the prothallium in a purely vege- 



* " Ueber ungeschlechtliche Keirapflauzeu an Farn-Prothallien," Botanische 

 Zeitung, 1874. 



