18 Varietäten, Descendenz, Hybriden. 



Bailey, I. W. and E. W. Sinnott. Investigations on the 

 Phylogeny of the Angiosperms, II, Anatomical evi- 

 dences of reduction in certain of the Amentiferae. (Bota- 

 nical Gazette. LVIII. p. 36-60. PI. III— V. 3 textfig. 1914.) 



The best way to give an idea of the contents of this important 

 paper is to copy the summary and conclusions published at '.he end 

 of this paper. 



The "aggregate" ray hj^pothesis developed by Jeffrey and 

 amplified by a number of students working under his direction 

 has an important bearing upon the phylogeny of the angiosperms, 

 since it indicates that certain of the Amentiferae are in all proba- 

 bihty the most primitive living representatives of the phj'lum. There 

 appear to be serious objections to this hypothesis,, however. 



a. Objections to the "aggregate" ray hypothesis. 



1. The phenomenon of chalazogamy, which was considered at 

 tirst of great phylogenetic value, cannot, in view of later investiga- 

 tions, be considered a reliable criterion for determining the phylo- 

 genetic Position of plants. 



2. The occurrence of so-called "aggregate" rays in the tertiary 

 does not appear to be significant, since "multiseriate" ra3^s, which 

 are considered to be a comparatively recent adaptation to the ad- 

 vent of a severe winter season and the consequent acquirement of 

 the deciduous habit, are found in middle and upper cretaceous 

 dicotyledons. 



3. If "aggregate" and "Compound" rays originated for the pur- 

 pose of storing the assimilates descending from the persistent leaves 

 of angiosperms in the warmer times of the Mesozoic and were later 

 replaced by "multiseriate" rays as an adaptation to a period of 

 refrigeration, we should hardly expect to find multiseriate rays well 

 developed in famiHes which have lived in tropical environments 

 since ancient times. 



4. The "aggregate" ray, which is comparatively infrequent, 

 characterizes the obviously reduced xerophytic Casnarhmceae, and 

 the temperate families Betulaceae, Fagaceae, and Ericaceae. 



5. The "aggregate" ray hypothesis does not account for the 

 development of "secondary" multiseriate rays nor for the origin of 

 wide rays in the root. 



6. The seedling evidence which has been advanced in favor of 

 the origin of wide rays from congeries of uniseriate rays is invali- 

 dated by the occurrence of wide multiseriate ra3'S in seedÜngs of 

 oaks, and also in such supposedly conservative regions in this 

 genus as the node, root, reproductive axis, and first annual ring. 



b. "Aggregate", rays stages in the reduction and disintegration 

 of wide multiseriate rays. 



In the Fatales and Casuarinaceae there is a very complete series 

 of forms in which the progressive reduction and disintegration of 

 wide multiseriate rays can be traced in detail. During this process 

 of reduction the wide rays appear usually at later and later stages 

 in ontogeny, until they finally disappear. The so-called "aggregate" 

 rays are stages in the disintegration of wide multiseriate rays. Sti- 

 mulating types of growth and injury recall the wide rays in regions 

 where they have been lost, and are frequently most effective in 

 those regions which are supposed to be conservative, such as the 

 first annual ring, root, node, and seedling. Stunted, suppressed. 

 poorly nourished types of growth, and severe distorting injuries 

 hasten the reduction and disintegration of the wide multiseriate- 



