270 MORPHOLOGY OF THE ANGIOSPERMS 



evidence for this theory. Some of the other types develop ontogeneti- 

 cally from anati-opous primordia. The basis for the opinion that the 

 orthotropous is the primitive type seems to be that it is apparently the 

 simplest type and that its usual position — basal and "terminal" on the 

 receptacle — is also simple. But it accompanies high specialization in 

 flower structiu-e. The Urticales show, in their various genera, the deriva- 

 tion of the orthotropous from the anatropous ovule. In the Ulmaceae 

 and Moraceae, the ovule is anatropous and suspended; Urtica and 

 Boehmeria have orthotropous, basal ovules; Laportea and other genera 

 are transitional. 



Ovule Number 



The primitive ovule number was doubtless several or many, as in the 

 Nymphaeaceae, Hydrocharitaceae, Butomus, Drimijs, Eupomatia. Re- 

 duction in number occurred with the restriction of the broad fertile 

 area of laminar placentation to two submarginal rows and, still further, 

 within the rows to one or two ovules, as carpel size was reduced. Rarely, 

 reduction to few or solitary ovules was directly from laminar, without 

 the intermediate submarginal stage — Cabombaceae (Fig. 85), Helo- 

 biales, Nelumbo, some Annonaceae, Winteraceae. Elaboration of the 

 placenta, with great increase of fertile surface— the development of 

 large emergences within the locule — was accompanied by multiplica- 

 tion of ovules to high numbers ( Fig. 80 ) , many more than in the primi- 

 tive carpel. Great numbers of ovules borne on large placentae are 

 present in the Ericaceae, Scrophulariaceae, Orchidaceae, Cucurbitaceae, 

 Gentianaceae, and other families. It has been estimated that the number 

 of ovules in an ovary of Cymbidium may be two million. 



Reduction in a single carpel to one or two ovules, with transitional 

 numbers, is seen in both laminar and submarginal placentation in many 

 families — Ranunculaceae, Rosaceae, Proteaceae, Nymphaeaceae, Legu- 

 minosae; similarly, within a locule in syncarpous ovaries — Liliaceae, 

 Claijtonia, Caryophyllaceae; within a group of related genera — Cijdonia, 

 Pijrus, Sorbiis. Reduction of the total number of ovules in a syncarpous 

 ovary to one ovule, usually basal, is frequent. These ovules represent 

 surviving members in syncarpous ovaries of complex structure. They 

 have usually been derived by reduction of free central placentae — 

 which, in turn, represent fused and modified axile placentae. Rarely, 

 basal ovules represent surviving members of parietal placentae, as in 

 the Droseraceae. 



The one or two ovules surviving in a follicle or achene are usually 

 proximal ones, but they are sometimes distal — some Proteaceae; rarely, 

 they are median members of the row. Evidence for the position of tliese 

 ovules is the frequent presence of vestigial ovules and, when these are 



