1242 



A TEXTBOOK OF THEORETICAL BOTANY 



B 



Fig. 1197.— Syngynia in A, Lonicera and B, Batis. {After Velenovsky and Le 



Maoiit.) 



genus Myrica and in Batis, which forms a monotypic family in the Centro- 

 spermae. There is also the case of Cryptocoryne, one of the Araceae, in 

 which the five naked, female flowers around the base of the spadix become 

 united and grow into a fruit which has all the appearance of having been 

 formed from five syncarpous carpels in one flower. 



It may be justly said that the essential feature of a carpel is that it is a 

 closed structure containing the ovules, but in some cases the closure is 

 incomplete. The best-known example is that of Reseda, in which the three 

 carpels are joined into a paracarpous ovary but their apices remain free. The 

 upper margins are stigmatic and soon separate, leaving the top of the ovary 

 open. A similar condition obtains in Salix, although only two carpels are 

 associated. This singular and, one might say, primitive, condition is prob- 

 ably secondary in the otherwise somewhat specialized flowers of Reseda, but 

 there are other instances in which this is less probable, because of the low 

 evolutionary status of the families in which they occur. 



Both ontogenetic and phylogenetic evidence leads to the belief that the 

 carpel was once an open structure which has become closed by marginal 

 union in a variety of ways. It is therefore of interest to find examples of 

 unclosed carpels in living families of a primitive grade. Such, for instance, 

 are the Winteraceae, closely allied to the Magnoliaceae, in which a morpho- 

 logical series, showing various degrees of closure, may be traced among 

 the genera. The most primitive type is Degeneria (Fig. 1198), a Fijian 

 genus, placed in a monotypic family, which has carpels formed like a con- 

 duplicate leaf, with long stigmatic margins, which only unite in the develop- 

 ing fruit. The stigmas extend as far inwards as the placentae, which are 

 laminar as in the following case. 



The Butomaceae, again, are primitive Monocotyledons, primitive, that 



