Observations on South African Plants. 31 



MOEPHOLOGICAL AND BIOLOGICAL OBSEEYATIONS 

 ON SOUTH AFBICAN PLANTS. 



By Db. S. Schonland. 



(Bead March 25, 1896.) 



1. A case of Peloria in a S. A. orchid (Disa patula ?). 



No order of plants exhibits such marvellous differences in the 

 shape of their flowers as orchids do, and yet their structure is 

 surprisingly uniform. In most orchids (and in all S. A. orchids) 

 the flower is composed of three sepals, three petals alternating with 

 the sepals, one stamen, and it has further a trimerous pistil. Of the 

 three stigmata which one would expect, two are usually confluent 

 and the third forms a peculiar structure called the rostellum. In 

 these orchids the single stamen is always placed opposite the odd 

 sepal, and the latter is originally always placed opposite the axis 

 from which the flower springs. * There are a number of reasons, 

 some of which will be found in the introduction to Mr. H. Bolus's 

 ' Orchids of the Cape Peninsula,' why we may ascribe theoretically 

 to the orchid flower two alternating trimerous whorls of stamens, of 

 which only one stamen is actually represented in most orchids, 

 namely, the odd one of the outer whorl, while a few orchids only, 

 such as the species of Cypripedium, possess the two lateral stamens 

 of the inner whorl. 



A great many plants which normally exhibit irregular flowers 

 sometimes produce regular or " peloric " flowers, and it is a pecu- 

 liarity of these peloria that they frequently have the structure which 

 one has theoretically ascribed to the normal irregular flower. I was, 

 therefore, greatly interested when I found amongst some flowers of 

 a Disa (D. patula ?), which Mr. B. Schlechter collected last year 

 near Humansdorp, one which had exactly the same diagram as the 

 one which had been theoretically constructed for orchids generally 

 by Charles Darwin and others. Peloria amongst orchids are very 

 common, and (as Mr. Bolus informs me) even in South Africa, but 

 such a theoretically nearly perfect case has not been put on record 

 from this part of the world, and I may, therefore, be allowed to 



* The diagram on p. 76 in Bolus's ' Orchids of the Cape Peninsula ' ought to be 

 reversed, in accordance with the usual practice of having at the top in such a 

 diagram the parts nearest the parent axis. 



