194 THE PATH OF DEGENERATIVE EVOLUTION 



In consequence, vegetable embryology is of little 

 use for investigation of the supposed backward path 

 of degeneration, for the rudimentary or reduced 

 organs of plants do not generally represent ancestral 

 stages. 



The seedling of Lathy rus tenuifolius (fig. 67), a 

 vetch, possesses rudimentary organs which cannot 

 be ancestral stages as their development is direct. 

 In this plant a whole series of leaves are formed 

 between those arising at germination and the adult 

 leaves. This intermediate series displays many 

 arrests of development. 



The adult leaf has a pair of stipules, foliage 

 leaflets, and tendrils (fig. 67, j). The leaves just 

 before these, have a pair of stipules (fig. 67, i), 

 which are absent in the leaves next before (fig. 67, 

 H). Still earlier leaves are produced with fewer 

 leaflets and tendrils (fig. 67, D-G), leaves without 

 leaflets and with a single tendril (fig. 67, c), and 

 leaves entirely without tendrils (fig. 67, B). Lastly, 

 at germination very rudimentary leaves are pro- 

 of the whole body, the branchial arches of mammals are employed 

 in the formation of important parts of the head and neck. The 

 tail of the tadpole is reabsorbed by phagocytes and its substance 

 used for the nutrition of the body. In the case of plants, such 

 occurrences are rare and limited ; the cells are enclosed in a rigid 

 wall which resists displacement or alteration ; the protoplasmic 

 contents may be absorbed and used as nutritive material by 

 another part, but the cellulose cell-wall remains. A useless organ 

 can be eliminated only at the expense of loss of material. 

 J. Massart, La Recapitulation et I' Innovation en enibryologie 

 vtgtiale (Bull. Soc. Roy. Bot. Selg., t. xxxiii., p. 150, 1894). 



