174 BOTANY. [CHAP. v. 



constituting the group, but only those that are most 

 pronounced and general, and for these reasons consi- 

 dered as being of value in indicating true relationship 

 and even these characters are not equally conspicuous 

 in all the included species, but gradually disappear and 

 are replaced by vestiges of other characters that in turn 

 become more pronounced, and constitute the leading 

 characteristics of a neighbouring section, hence book 

 characters only cover the most typical representatives of 

 a given allied group of plants, and it is often a matter of 

 personal opinion as to which of two or more sections 

 certain plants should be placed in, that occupy the 

 neutral or transitional line between one section and 

 another, by possessing, as stated above, the dying out 

 characteristics of one group, and the incipient indica- 

 tions of those which in the fully evolved condition con- 

 stitute the marked features of an allied group. 



The above remarks apply to the two primary divisions 

 of the Vegetable Kingdom as given above. Cryptogams 

 and Phanerogams do not constitute two sections allied 

 to each other by the broad ties of plant individuality 

 only, such as the presence of chlorophyll and consequent 

 power of feeding on inorganic matter, but in the closer 

 affinity indicated by numerous points of agreement in 

 matters of detail; in fact, Cryptogams, as the oldest 

 section in point of time, appears to have emphasized two 

 points in its evolution that stand out conspicuously in 

 the higher types, namely, alternation of generations, 

 which implied the breaking up of the complete life- cycle 

 of an individual into two phases, one sexual, the other 

 asexual ; the second feature is the presence of motile 

 male bodies or antherozoids ; an additional negative 



