FOLIATION. 23 



Ginkgo they are almost of circular form ; in Sciadopitys they are 

 alternate and not whorled like the phylloid growths that perform the 

 functions of leaves in older plants ; in Pinus they are solitary,. 

 and not in clusters of two or more.* In the Cupressineaa the 

 primordial leaves are often produced for many years in succession,. 



and are thence frequently seen 

 simultaneously with the adult 

 foliage as in Juniperus, Thuia, 

 Cupressus (section Chamsecy- 

 paris'. In these genera, and in 

 a remarkable variety of Cryp- 

 tomeria japonica known in 

 gardens as C. elegans, there are 

 forms in which primordial leaves 

 only are produced during the 

 whole life of the plant, f 



Narrowness in comparison 

 with length is the prevailing 

 characteristic of the adult 

 foliage of the majority of the 

 species cultivated in Great 

 Britain, the exceptions occurring 

 chiefly in the Cupressinese with 

 heterornorphic foliage, of which 

 the adult form is small, scale- 

 like, almost as broad as long, 

 especially on the terminal 

 growths. A more conspicuous 

 exception is Ginkgo, in which 

 the leaf expands into a fan-like 

 blade that is usually much 

 broader than long but with- 

 out any true midrib ; the 

 numerous veins of nearly equal 

 size diverge from the top of 

 the stalk and are unconnected 

 by any lateral reticulations. 

 Notwithstanding the prevailing 

 narrowness in comparison with length, there is a considerable 

 diversity in the shape of the leaves in the different genera, and 



* The protomorphic leaves of Pinus should not be confused with the metamorphosed 

 primordial leaves of the adult foliage, which consist of small membraneous envelopes, 

 called for convenience of description "basal sheaths." 



t These forms, often called in gardens "juvenile," can only be perpetuated from cuttings. 



l-'ig. 8. Young plant of Libocedrits decurrens. 

 c, cotyledons ; PR, primordial, TR, transitional leaves 

 AD, adult foliage. 



