66 HENRY S. CONARD 



On the other hand, the leaves of ferns and angiosperms and 

 the older Cordaitales and Cycadales, are usually large and con- 

 spicuous (megaphyllous) . Small leaves are in all cases clearly 

 modifications of the former type. The sporangia in nearly all 

 the lower forms are numerous, and on the back of the leaf 

 (abaxial). Profound modifications of this character occur in 

 Angiosperms. Wherever a leaf is attached to the stem in all of 

 this great group of plants, the vascular tissues of the stem bend 

 out bodily to form the leaf trace. In hollow cylindrical vas- 

 cular systems, this leaves a gap in the cylinder — a leaf gap 

 (phyllosiphonic) . 



In view of the importance of these distinctions, it is imperative 

 that at this point, at least, classification must be immediately 

 adjusted to the present morphological conclusions. And if the 

 profoundest cleavage in the higher plants lies between the 

 Lycopsida and Pteropsida, then we must put into the back- 

 ground such terms as Pteridophyta and Spermatophyta. Nothing 

 may be permitted to obscure this major conclusion. 



In our present imperfect knowledge of the fossil Tracheata, 

 we are unable to separate sharply between the fern-like seed 

 plants and the seed-plant-like ferns. Apparently this separation 

 is destined to become more obscure with increasing knowledge. 

 We are therefore justified in co-ordinating the ferns and gym- 

 nosperms. The evidence tends also to close the gap between 

 gymnosperms and angiosperms. There are left, therefore, in the 

 Pteropsida three co-ordinate groups. The nomenclature of 

 these groups and their subdivisions presents some awkward 

 difficulties. 



According to International Rules, groups of ordinal rank have 

 names ending in -ales. Names of sub-orders end in -ineae, of 

 families in -aceae, of sub-families in -oideae, of tribes in -eae, and 

 of sub-tribes in -inae. This has become current usage in the 

 classification of angiosperms. The results are so satisfactory 

 that the terms have met with general acceptance, and there is 

 even a surprising unanimity regarding the limits and contents 

 of the many orders and families. It would obviously be folly 

 to criticise or attempt to change this usage as applied to dicoty- 



