VASCULAR CRYPTOGAMS 11 



with a cell-wall of cellulose, and thus becomes an oosperm, w r hich 

 develops into the embryo, and finally into the sporophyte, which 

 is often of great size and extended length of life. It is this that is com- 

 monly known in popular language as the Fern, Club-moss, &c. On it 

 are produced, without any process of fertilisation, the spores, which are 

 always single cells, protected by two or three coats, and giving rise on 

 their part, when they germinate, to the oophyte. This is the cycle of 

 development in the Isosporous families of Vascular Cryptogams. In the 

 Heterosporous families there are produced (always on the same plant) 

 two different kinds of spore, differing very greatly in size larger mega- 

 spores and smaller microspores. The former produce female prothallia, 

 that is, those which bear archegones only ; the latter male prothallia, 

 bearing antherids only, or even antherozoids, without the intervention of 

 a male prothallium or antherid. The spores are always endogenous 

 structures, produced by free-cell-formation within a spore-case or 

 sporange, which again, in the heterosporous families, is a megasporange 

 or a microsporange, according as it contains megaspores or microspores. 

 The sporanges are often collected into groups known as son, and these 

 may again be enclosed within special chambers, sporocarpsmconceptades. 

 Various kinds of vegetative propagation, similar to those of Flowering 

 Plants, also occur on both oophyte and sporophyte ; and in certain ex- 

 ceptional cases either the oophore or the sporophore may be entirely 

 suppressed, constituting the phenomena of apogamy and apospory re- 

 spectively. These will be described especially under Ferns, where they 

 are of the most common occurrence. 



It may be useful in this place to compare the structure of the organs 

 of reproduction and the phenomena of impregnation in Vascular 

 Cryptogams with those of Phanerogams, and to endeavour to trace the 

 requisite homologies, 1 although these cannot be fully understood with- 

 out some knowledge of the details of structure described under the 

 separate families. It has been usual to compare the pollen-grain of 

 Phanerogams with the antherozoid of Vascular Cryptogams ; but this is 

 not strictly accurate. The essence of the act of fecundation consists in 

 the coalescence of the protoplasmic contents of an active (male) and of 

 a passive (female) cell. The protoplasmic endoblast or cell-contents in 

 each case must, therefore, be homologous ; that is, the antherozoid with 

 the protoplasmic contents of the pollen-grain which, in Flowering Plants, is 

 brought into contact with the embryonic vesicle by means of the pollen- 



1 Hofmeister was the first to point out these homologies in his Vergleich. Unters. 

 iiber Keimungu.s.iv. der hoheren Kryptogamen (see the Ray Society's translation, On 

 the Germination, &*<:., of the Higher Cryptogatnia, p. 438). They have since been 

 traced out more completely by Hanstein, Celakovsky, and others. 



