134 THE LIVING CYCADS 



leaf of the seedling in some cases not reaching more than 

 a tenth of the length of the leaves of adult plants. The 

 number of leaflets is smaller. In Ceratozamia the first 

 leaf usually has four leaflets, while the leaves of large 

 plants may have as many as a hundred leaflets. The 

 number of leaflets increases steadily as the plant becomes 

 larger, until, in this respect as in the case of the number 

 of leaves in a crown, it attains the approximate norm 

 of the species. 



In seedlings the margin of the leaflet often differs 

 strikingly from that of the leaflet of an old plant, ^ioon 

 edule may be taken as an example (Figs. 74-76). The 

 leaflet in the seedling has a spiny margin, the spiny char- 

 acter being most conspicuous during the first four or 

 five years; the number of spines then diminishes slowly 

 but does not disappear completely until the plant has 

 reached an age which may be estimated at" twenty or 

 thirty years. 



In this connection it is interesting to note that the 

 seedling leaves of Dioon spinulosum have the same spiny 

 character, but that the plant retains it as long as it lives. 

 Many would regard this as an illustration of recapitula- 

 tion — ontogeny recapitulates phylogeny, or the history 

 of the individual is the history of the race — and would 

 claim that Dioon edule is the offspring of D. spinulosum, 

 and that D. edule in its earlier development is passing 

 through a stage which characterized its ancestor. In 

 the case of Encephalartos Altensteinii and E. coffer a 

 difference in leaf margins is enough to confuse a tax- 

 onomist in his diagnosis. E. Altensteinii has leaflets with 

 spiny margins, and the character is supposed to persist 

 throughout the life of the individual. E. coffer showfe 



