COXIFE RALES 



55 



of seedlings bear foliage leaves, which may disappear from the 

 long shoots in the second year, as in P. silvestris, or may con- 

 tinue for many years. These needlelike primary leaves are of 

 simpler anatomical structure than the subsequent foliage leaves, 

 especially in the matter of provision for controlling transpira- 

 tion. In the juvenile forms 

 of Larix the leaves persist 

 during the winter. It is 

 among the Cupresseae, how- 

 ever, that the greatest amount 

 of work has been done in " fix- 

 ing " juvenile forms, such 

 relatively permanent forms 

 being known in gardens as 

 species of Retinospora. While 

 some of the adult forms of Cu- 

 presseae, as Juniperus com- 

 munis, retain the more primi- 

 tive habit of spreading nee- 

 dles, others (Juniperus Vir- 

 giniana, species of Cupressus, 

 of Callitris, of Cliamaecy- 

 of Thuja) develop 

 leaves upon 



their adult shoots that is, 

 leaves whose upper sides have 

 become organically connect^ 

 ed with the adjacent stem sur-' 

 face, so that they appear as 

 <>rof'n scales. In such cases, 

 the juvenile form, with its 

 spreading needle leaves, pre- 

 sents a striking contrast with 



the adult form (Fig. 42, .4-#). FlG . iO.Araucana sp.-Atter COILTEP, 



In Pliyllocladus the phyllo- 



clads are in the axils of small scalelike leaves which are at first 

 green, but later become true scales, and are really the trans- 

 formed primordia of foliage leaves; while in the juvenile forms the 

 first leaves are flat green needles, which are gradually replaced by 

 shorter and shorter ones until the adult form is reached, and the 

 5 



pans, 



" concrescent 



