1490 



A TEXTBOOK OF THEORETICAL BOTANY 



Urticaceae, Cruciferae, Rosaceae, Malvaceae, Convolvulaceae, 

 Fagaceae, Juglandaceae, Rubiaceae, Labiatae. 



BASAL 







RUDIMENTARY BROAD 



CAPITATE LATERAL 



PERIPHERAL 







PERIPHERAL 



Linear Subdivision 



AXILE 



Miniature Subdivision 



LINEAR 



Q§ 



DWARF 



Foliate Subdivision 



MICRO 



• ® • 



SPATULATE 



BENT 



FOLDED 



INVESTING 



Fig. 1362. — Martin's twelve seed types in diagram- 

 matic form. {After Martin.) 



Martin traces certain lines of organizational advance among these types, 

 considering the seeds as organisms in their own right, whose evolution may 

 be viewed independently of the general evolutionary advance of the plants 

 which produce them (Fig. 1363). Thus he considers that large seeds with 

 small embryos are relatively primitive and that evolution has proceeded 

 divergently towards quantity (of seed produced) on the one hand (Reduced 

 Division) and towards quality on the other (Foliate Division). The high 

 degree of insulation of the seed certainly justifies its treatment as a micro- 

 cosm and its evolution along independent lines of advance has parallels 

 among other organs of the vegetative plant. 



The term aril is applied in its widest sense to all external outgrowths or 

 "effigurations" of the seed, especially those which arise after fertilization 

 (Fig. 1364). It is not easy to delimit exactly the application of the name. 

 Logically it should include hairs, but in practice these are not usually 

 treated as arils, not even the copious development of plumed hairs on the testa, 

 which are of value in wind dispersal, although they are definitely arillar 

 in nature. Nor are wing-like extensions of the testa usually included. The 

 aril is therefore strictly something extra, something hypertrophic and dis- 



