A GENERAL SURVEY 5 



consists in the production of spores from which 

 arise independent organisms responsible for the 

 sex elements. These bodies, which are called 

 prothalli, are an essential feature in the life 

 history of the ferns, the club mosses and the 

 horsetails. In the case of some vascular 

 cryptogams two kinds of spore are produced, 

 and in such instances it is common to find that 

 two sorts of prothalli are developed, each of 

 which bears cells of a distinctive sex character. 



Although at first sight the plan of repro- 

 duction which is evinced in the flowerless 

 plants may seem to be far removed from that 

 adopted by the species producing blossoms, yet 

 it will be possible to show that the difference 

 is more apparent than real. Indeed, the con- 

 sideration of the connecting links between the 

 two great sections into which the world of 

 vegetation has been divided is not the least 

 interesting side to a study of the flowerless 

 plants. At the moment it is, perhaps, as well 

 to complete our survey of the remaining groups 

 which follow the highly organised plants to be 

 found amongst the ferns, the club mosses and 

 the horsetails. 



It has been seen in the case of the vascular 



