COXIFERALES 



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 Larij: 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 Eefinospora. While 

 some of the adult forms of Cu- 

 presseae, as Juniperus com- 

 munis, retain the more primi- 

 tive haljit of spreading nee- 

 dles, others {Jun iperus Vir- 

 giiiiana, species of C'upresstis, 

 of Calhh'is, of Chanutecy- 

 paris, of Tliuja) develop 

 " concrescent " leaves ujjim 

 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 

 green scales. In such eases, 

 the juvenile form, with its 

 spreading needle leaves, pre- 

 sents a striking contrast with 

 the adult form (Fig. 42,4-1;). 

 In FhyUodadiis the phyllo- 



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

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

 foi'med primordia of foliage leaves; while in the juvenile forms the 

 first lea\'es are flat green needles, which are gradually rejdaeed by 

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



Flu. 40.- 



