294 DR. M. T. MASTERS ОМ SOME POINTS ІМ 
in a line continuous with the floral axis, although he admitted that in Primulacez there 
are grounds for supposing the placenta to be truly axial *. 
'The appearances presented by the double Primrose sent by Miss Dowson substantiate 
the view of Van Tieghem, that the placenta is derived from the carpellary leaf by 
chorisis (Pl. XXXIX. figs. 34-38). In the specimens in question the placentas are 
sometimes marginal, at other times parietal, the placenta in this latter сазе being 
homologous with the midrib of а carpellary leaf, and not unfrequently detached from it, 
sometimes slightly, at other times completely (Pl. XXXIX. figs. 37, 38). Double- 
flowered Primulacez in fact frequently furnish illustrations of free central, axile, mar- 
ginal, and parietal placentation (Pl. XL. fig. 16). Moreover they show that in some 
cases the placenta, whatever its position, is a mere outgrowth from the carpellary leaf, 
capable of becoming completely detached from it, and in that case simulating an axis. 
In a malformed Cowslip, a figure of which is given (Pl. XL. figs. 17-20), among 
other changes the pistil was broken up into its five carpels, each with its style and stigma. 
In the centre of the flower was а mass of threads or funicles, each surmounted by an 
imperfect ovule. Some of these threads evidently sprung from the inner surface of the 
сатре]з, others from the margins, while the majority were quite detached from the car- 
pellary leaf. 
In the normal flower this detachment must take place, if at all, at а very early period, 
and the placentary ribs of one carpel may become united to those of another, and so, at 
length, a free central placenta may be formed. If the axial appearance of the placenta 
and the five vascular bundles visible in it be cited as proof of its axial nature, it may 
be pointed out that five petioles, each with a single vascular bundle and united together, 
would give an appearance of an axis. 
For my own part, I look on the alleged distinction of axial and appendictlar organs as 
one of convention, desirable to be kept up for descriptive or classificatory purposes, but 
altogether of secondary importance from a morphological point of view. The occurrence 
of leaf-buds or flower-buds on the placenta, such as have been recorded in various 
monstrous Primulacee, therefore has not for me the same degree of significance that 
it has for those who look upon their presence as indicative of the axial nature of the 
organs bearing them.  Leaf-buds, flower-buds, and roots may and do arise from leaf- 
organs or phyllomes, as they do from caulomes, and they cannot be looked on as abso- 
lutely characteristic of either +. 
* In the female flower of an Alder (Alnus) sent to me by Mr. Stratton, among other changes, the ovules were borne 
- on a stalk standing up free in the centre of a one-celled pistil, forming a free central placenta. It seemed probable 
that in this case the stalk was composed of the detached dissepiments of the ovaries. 
+ AsI write Ihave before me a flower of Calochortus sent me by Mr. Burbidge, in which the filament of the 
н bears at its junction with the anther a well-marked bud (Pl. XL. fig. 21). These adventitious buds are 
sometimes veritable enations; at other times they are borne on stalks which are congenitally adherent to to the leaf- 
organ. Зее Planchon, * Quelques mots sur les inflorescences epiphylles,” Mém. Acad. Stanisl. 1862, p. 403; Caspary, 
Schrift, phys.-ckon. Gesellsch. zu Kénigsberg, 1874. Still more germane to the subject now under consideration 
are those cases in which the placenta bears leafy ovules, as happens occasionally in Crucifers. In a species of 
Triumfetta, and in one of Corchorus, I have seen a similar arrangement, the latter case (РІ. XL. figs. 21-24) being | 
particularly ерт ев the position of the leafy ovuleson the midribs of the — not on the margins. 
