134 



PRINCIPLES OF PLANT- TERATOLOGY. 



sents an excavation of the receptacle (!) cannot here 

 be followed. If it were so that would indeed be an 

 anomaly in the vegetable kingdom, for no parallel case 

 to a phenomenon of that kind can anywhere be found. 

 That the spur is really part of the posterior sepal is 

 shown by Pelargonium, a near ally of Tropceolum, in 

 which the spur is undoubtedly an outgrowth of this 

 sepal. 



In Pelargonium, besides the posterior sepal (no. 2 

 in the order of development), sepals 1 and 3 have also 

 been seen spurred. 



Where all five sepals, as in Delphinium and Aconitum, 

 are spurred, we have " true pelory," i. e. a change from 

 the irregular or zygomorphic to the regular or actino- 

 morphic flower, for it is to the presence of a spur in 

 oue of the sepals only that the zygomorphic condition 

 is due. 



Then there are the rare cases in which spur-forma- 

 tion occurs in the calyx, where, under ordinary con- 

 ditions, this whorl is quite devoid of such structures. 



Sommier and Hemsley describe spur-formation in 

 the lateral sepals of a butterfly-orchis (Via tan fit era 

 chlorantha var. trica lea rata*) (PI. XLII, fig. 2). 



Loss of Spur. — The converse change occurs when 

 the posterior sepal completely loses its spur, so that it 

 comes to resemble the remaining sepals. Here we see 

 a second type of " pelory." This has been noted in 

 Delphinium, Aeon it urn, Pelargonium (a terminal flower), 

 the canary-creeper {Tropseolum aduncum), and T. ma jus 

 (fig. 117). In these the flowers were either terminal of 

 lateral ; in the first-named species some of the flowers 

 remained partially irregular owing to lack of modifica- 

 tion of the corolla. 



Zi/goniorphy. — Hildebrand and Vidal both observed 

 remarkable, irregular flowers of Fuchsia in which, 

 along with other changes in the corolla, the posterior 



* Phenomena of this kind represent what is known as " false pelory/' 

 because the foliar organs which take part in it are not all of the same kind 

 (in this instance two sepals and one petal). 



