228 THE MICROSCOPE AND ITS KEVELA.TION8. 



an act of growth; and although, in the first case, the setting-free of the 

 ' swarm-spores ' from the parent-cell calls into existence a fresh brood of 

 secondary organisms, this is no more to be regarded in strictness as a 

 'new generation/ than is the put ting-forth of a new set of leaf -buds by 

 a tree every one of them, when separated from its stock, developing 



itself under favorable conditions 

 i n * ^ ne ^keness of that which 

 produced it. As a 'new gen- 

 eration,' in any Phanerogamic 

 plant, has its origin in the fer- 

 tilization of a highly specialized 

 ' germ-cell ' (contained within 

 the ovule) by the contents of a 

 'sperm-cell' (the pollen-grain) 

 so do we find among all save the 

 lowest Cryptogams a provision 

 for the union of the contents of 

 two highly specialized cells; the 

 'germ-cells' being fertilized by 

 the access of motile filaments 

 (antherozoids), set free from the 



Successive stages of free Cell-formation in Em- P f, v ifi p( j n f fl-, A ( ara rrn nolle ' 

 bryo-sac of Seed of Scarlet-runner ;-a, a, a, com- Cavities OI tlie Sperm-CCliS 

 pleted cells, each having its proper cell-wall, nucleus, within which tllCV WCl'C develop- 

 andendoplasm. lying in a protoplasmic mass, through A /fi OKOX n n i ui^. 

 which are dispersed nuclei and cells in various stages ea ( /coy). >Ut altnOUgn the 



of development. sexual process can be traced 



downwards under this form 



into the group of Protophytes, we find among the lower types of that 

 group a yet simpler mode of bringing it about; for there is strong reason 

 to regard the act of 'conjugation,' which takes place among the 'unicel- 

 lular' AlgcB ( 229, 235), in the same light, and to look upon the 

 'oospore' 1 which is its immediate product, as the originator (like the 

 fertilized embryo-cell of the Phanerogamic seed) of a ' new generation.' 



226. In the lowest form of vegetation, every single cell is not only 

 capable of living in a state of isolation from the rest, but even normally 

 does so; and thus the plant may be said to be unicellular, every cell having 

 an independent 'individuality.' There .are others, again, in which 

 amorphous masses are made up by the aggregation of cells, which, though 

 quite capable of living independently, remain attached to each other by 

 the mutual fusion (so to speak) of their gelatinous investments. And 

 there are others, moreover, in which a definite adhesion exists between 

 the cells, and in which regular plant-like structures are thus formed, 



1 The term spore has been long used by Cryptogamists to designate the minute 

 reproductive particles (such as those set free from the * fructification ' of Ferns, 

 Mosses, etc.), which were supposed in the absence of all knowledge of their 

 sexual relations to be the equivalents of the Seeds of Flowering plants. But it is 

 now known that such 'spores' have (so to speak) very different values in differ- 

 ent cases; being, in by far the larger proportion of Cryptogams, but the remote 

 descendants of the fertilized cell which is the immediate product of the sexual 

 act under any of its forms. This cell, which will be distinguished throughout the 

 present treatise as the oospore, is the real representative of the ' primordial cell ' 

 of the ' embryo' developed within the seed of the Flowering plant. On the other 

 hand, the various kinds of non-sexual spores emitted by Cryptogams, which have 

 received a great variety of designations, are all to be regarded (as will be pres- 

 ently explained) as equivalents of the leaf -buds of Flowering plants. (See the 

 next Note.) 



