258 GTMNOSPEBMJ:. 



4. The number of carpels in each flower varies from one to 

 many, most frequently three, of which the central one remains 

 sterile. 



5. Each carpel bears only one ovule. The flower which is 

 formed of only one carpel appears to consist of only one ovule. 



6. The ovule has in Taxaceae either a double integument 

 (Podocarpese, Taxeae), of which the external is the " aril," or, as 

 in the Cycadeae, a single one, which is homologous with the two 

 united together. 



7. The external integument in the Pinoideae is expanded to 

 form a leaf -like structure the ovuliferous scale and bears on its 

 dorsal side the ovules, which are thus only provided with one, and 

 that the inner, integument. 



This later interpretation of the female cones in the Conifera is more pro- 

 bably correct than the older ones ; that, however, which appeared in the former 

 issues of this book, may also be stated. It was to the effect that each catkm- 

 like female cone is in reality a single flower ; the cone-scales in the Cupressacefe 

 were single leaves, namely carpels, which bore the ovules on the side which is* 

 turned upwards; the division into two parts which makes its appearance in the 

 other orders, and becomes most prominent in the Abietaceae, was compared 

 with the division of a leaf into a barren and a fertile portion, which is fouudi 

 especially in Ophioglossacese and Marsiliacese, or with the ligule in Isoetes. 



POLLINATION is accomplished by means of the wind. At the- 

 period of pollination the leaves are always so widely separated 

 from one another, that the ovules can catch the pollen-grains- 

 carried to them by the wind ; this is often effected by the mucila- 

 ginous drops which appear at the micropyle, and by the evapo- 

 ration of which the pollen-grains are brought in contact with 

 the nucellus. The entire cone grows considerably as soon as- 

 fertilisation has taken place, and the cone-scales in Pinoidese 

 close together so that the seeds while maturing are enclosed, and 

 it is not until the seeds are ready for distribution that the cone- 

 scales again become separated. In the Pinoideay, the fully deve- 

 loped ovuliferous scales are hard and woody ; and in this condition 

 the collection of female flowers is termed a cone. In the Taxoidese, 

 true cones are the exception. 2-15 cotyledons are present, ar- 

 ranged in a whorl. 



The characteristic feature of this class is the abundance of 

 resin, which is to be found in isolated cells (especially in ther 



