PROPAGATION AND CULTURE. 13 



are, when young, furnished with a membranous scale-like 

 cover. 



The subject of internal structure we may here pass over 

 with the remark that the Ferns belong to the lowest group 

 of vegetation, which is especially remarkable for its loose 

 and often succulent texture, owing to the absence, or the 

 paucity, of those tissues which give firmness and elasticity 

 to the higher orders of plants. The Ferns, however, are the 

 highest members of this lower group, and hence we find 

 them possessing, to some extent, both woody and vascular 

 tissue, mixed up with the more succulent cellular tissue 

 What these tissues are, may be found explained in any 

 elementary book on physiological botany. 



CHAPTER IL 



PROPAGATION AND CULTURE TOPOGRAPHICAL ASPECT USES PRE- 

 SERVATION FOR THE HERBARIUM. 



NATURALLY Ferns are propagated by means of the spores. 

 These spores, which are somewhat analogous^o seeds, being 

 like them endowed with that mystery the vital germ, when 

 placed under fitting conditions, become developed into young 

 plants ; but they differ from seeds in some important par- 

 ticulars. 



All true seeds have a determinate structure. They have 

 an embryo, provided with special organs ; there is the plu- 

 mule, or germ of the descending axis, the origin of the stem, 

 and there is the radicle, or germ of the descending axis, the 

 origin of the root. When a seed is planted, in whatever 

 position it may chance to have been deposited in the soil, 

 the young root or radicle strikes downwards, and the young 

 stem or plumule grows upwards. 



The Fern spores have none of these determinate parts, 

 but are, as it were, homogeneous atoms ; and when placed 

 under circumstances which induce germination, that part 

 which lies downwards produces the root, and that part 

 which lies upwards produces the rudimentary stem. The 

 spores themselves are minute vesicles of cellular tissue. As 

 they grow, this vesicle becomes divided into others, which 

 again multiply and enlarge, until they form a minute green 

 leaf like primordial scale or germ-frond, technically called 

 the prothallus. From this the axis with its roots and stem 

 are eventually developed, 



