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ANATOMY, AND LIFE-HISTORY OF THE CONIFER JE. 



323 







while Cunninghamia and Sciadopitys have several. All the 

 Abietineae have two ovules only. 



The relative position of the ovules and their arrangement 

 when reduced in numbers have been alluded to under the head 















of Sciadopitys. Mention may also here be made of the arrange- 

 ment of the ovules in Callitris and Cupressus. In the young 

 state the ovules are crowded at the base of the fruit-scale, but 

 as the scale grows older it grows in length and the ovules are 

 carried up with it. An examination of the ovules in these 

 plants or of the scars whence they have fallen, seems to show 

 that the arrangement is one of decussating pairs, modified by 

 pressure and compulsory arrangement in one place : thus two 

 lateral ovules are succeeded by one median one, its fellow being 

 suppressed ; above the median ovule come two more lateral 

 ones, and so on. In the Sciadopitys just alluded to the arrange- 

 ment was centrifugal or cyrnose. 



As the ovules ripen into seed they sometimes becomes fleshy ; 

 thus the seeds of Ginkgo, Cephalotaxus, and Torreya (fij;s. 28 

 and 29) closely resemble those of Cycas, there being a fleshy 

 covering enveloping a woody shell, within which is the perisperm 















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Fig. 28.— Seed of Torreya grandis and sections, 



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(prothallus), covered by a thin membrane adherent beneath to the 

 woody shell, so that on opening the latter the lower part of the 

 perisperm is bared, while the upper part is clothed with a 

 membranous cap exactly us in Cycas. 







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