An Historical Sketch. 67 
organ as in fact representing the homologue of a segment or leaflet of the 
carpel which bears it (Fig. 3). 
The notable founder of this view of the matter is Brongniart (9), who 
in 1844 made in the first place observations on abnormal carpels of Del- 
phinium e latum, and noted the occurrence of transitions between the triden- 
tate lobes of the foliaceous carpel and the ovules themselves. In his con- 
clusions formulated from these facts he says that the veins of the placenta 
are really the lateral veins of the carpellary leaf ; each ovule corresponds to 
a lobe or a large tooth of this leaf, while the funicle, as also the raphe, is 
formed by the median vein of this lateral lobe ; the outer integument is 
the terminal portion of this leafy lobe folded on itself and forming a hood, 
the nucellus being a new production — a cellular protuberance arising on the 
upper surface of this lobe. It is thus impossible to regard the ovules 
together with the placenta as a production distinct from the carpellary 
leaf, and as part of the main or lateral axis. In Brassica Napus again, 
he observed transitions between the ovary and two foliage-leaves, and 
between the ovules and lobes of the leafy carpel. In abnormal ovaries of 
Anagallis arvensis the ovules are represented on the axial placenta by tiny 
leaves. In this case he evidently regards the ovules as the homologues of 
entire leaves, and also states his belief in a double origin for placentas : 
from the margins of carpels and from a prolongation of the floral axis. 
Finally, his estimation of the value of abnormalities, in the opening words 
of the paper, are worth quoting : ‘ There is hardly a botanist at present who 
does not recognize how much light the study of these aberrations from the 
normal structure, to which the name of monstrosities is given, sheds on the 
essential and fundamental structure of certain parts of the plants, or on that 
which is peculiar to certain groups of plants.’ 
Robert Brown (35), in his paper on Rajflesia (p.211), says: ‘ The principal 
point in which the antherae and ovaries agree, consists in their essential 
parts, viz. the pollen and ovula, being produced on the margins of the 
modified leaf.’ On p. 21 1 he says further: ‘The marginal production of 
ovula not infrequently becomes apparent where its formation is in some 
degree imperfect, and is most evident in those deviations from the regular 
structure where stamina are changed more or less completely into pistilla,’ 
as in Sempervivum tectorum , &c. On pages 379 and 556 of the first 
volume of his Miscellaneous Botanical Works he speaks of the margin 
of the carpels as the proper place for ovules, and he gives instances of 
exceptions to this rule, as in Nymphaeaceae, Mesemhryanthemum. On 
p. 563 we find the remark that ‘ovules belong to the transformed leaf 
or carpel, and are not derived from processes of the axis united with it, 
as several eminent botanists have lately supposed. That the placenta 
and ovula really belonged to the carpel alone is at least manifest in all 
cases where stamina are changed into pistilla.’ 
