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A TEXTBOOK OF THEORETICAL BOTANY 



The group of families formerly called the Amentiferae contains many 

 examples of integumental vasculation, which as we mentioned above is 

 regarded by some authors as a sign of their primitive status. Some also 



Fig. 1289. — Myrica £;ale. Longitudinal section of the fruit and contained ovule. 

 A, Style. B, Adherent bract. C, Vascular bundle of bract. D, Integument. 

 E, Vascular bundle of integument. F, Nucellar stalk. G, Main vascular 

 supply. H, Nucellus. I, Embryo sac. J, Nucellar strand of conducting cells 

 leading to embryo sac. {From Kershaiv, "Annals of Botany", 23.) 



show nucellar vasculation. In Carpinus and Castanea true tracheids are 

 found below the embryo sac, but there is no connection with the chalazal 

 bundle. Casuarina has a chalazal strand which extends up in the nucellus 

 to the base of the sporogenous tissue, some of the cells of which lignify 

 and prolong the conducting tissue upwards. These plants are in many 

 respects primitive, but nucellar vasculation also occurs, either regularly or 

 sporadically, in some plants of quite advanced families, such as Asclepia- 

 daceae, Capparidaceae, Euphorbiaceae and Agavaceae. 



The micropyle, the apical opening which gives access to the nucellus, 

 may be formed either by the inner integument only or more rarely by the 



