574 
PHANEROGAMS. 
own observations on Chenopodiaceae and Polygonaceae, but they also warrant 
the assumption that the ovules previously described by Payer as terminal are 
really so. Since, however, it is not my object here to enter into a detailed proof 
of theoretical matters, it will be sufficient for the present to summarise the various 
phenomena. 
With respect to position, the following classes may first of all be distinguished: — 
A. Ovules produced on the Carpels and springing from the carpellary leaves ; 
and either 
1. Marginal, from the reflexed margins of the carpels (Figs. 385, 386, 
387, 390); or, 
2. Superficial, from the whole of the inner surface of the reflexed halves 
of carpellary leaves, always apparently with the exception of the 
mid-rib of the carpellary leaf (Fig. 357, 382). 
3. Axillary or basal, arising from the base of the upper surface of the 
carpel or in the axil of the carpel {^Ranunculus, Sedum, Zanichellia 
according to Warming'). 
' See Warming, Rech, sur la ramification des Phanerogames, Kopenhagen 1*^72, p 22. Tab. XI. 
fig. i-io. Axillary ovules are no more to be regarded as buds (caulomes) than are the axillary 
sporangia of Lycopodinm. 
[The question of the morphological significance of the placenta and of the ovule is one which 
has been much discussed of late. With regard to the placenta, Schleiden, starting with the concep- 
tion of the ovule as being a bud, considered the placenta to be necessarily an axial structure, 
inasmuch as only axial structures normally bear buds (Princip'es of Scientific Botany, 1849, 
pp. 382 ff.), a view which was adopted and developed more especially by French botanists (see 
Payer, Organogenic). According to a second view, the placenta is a portion of the carpel itself, 
usually of its margin, that is, that it is always boine by a leaf. This view has been revived of late 
years by Van Tieghem (Rech, sur la structure du pistil, 1871), by Celakovsky (Ueb. Placenten und 
Hemmungsbildungen der Carpelle, Sitzber. der k. böhm. Ges., Prag, 1875 ; Vergl. Darstellung der 
Placenten, ibid. 1876), by Braun (Bemerk, ueb. Placentenbildung, Sitzber. d bot. Ver. d. prov. Brand. 
1874), and Eichler (Blüthendiagramme, II. 1878) has now accepted it. In spite of all that has been 
written in support of these two theories, it cannot be admitted that either of them satisfactorily 
explains every possible case: if the former must evidently be forced when it is applied to a case of 
parietal placentation, this is equally the case with the latter when it is applied to free-central placen- 
tation, as in the Primulaceee. Both these attempts at generalisation seem to be too arbitrary. In 
consequence a third view has been promulgated, more especially by Huisgen (Untersuch, ueb. die 
Entwickelung der Plncenten, Bonn 1873) and formerly held by Eichler (Blüthendiagramme, I. 1875), 
that the nature of the placenta is not the same in all cases. In the Primulacese, for instance, it 
belongs to the floral axis, and, according to Huisgen, this is also the case in certain instances of 
axile placentation, as in the Solanacese, Lobeliacege, Ericaceae, Malvaceae, and Hypericaceoe, the 
placenta in these orders being a prolongation of the stem ; it also belongs to the axis in such forms 
as the Piperaceoe, in so far as any placenta can be said to exist in them at all : in the Violacece and 
Leguminos^e and in Monocotyledons the placenta is a development of the carpels : finally, in Cruci- 
ferse and Resedacese, and, according to Barcianu, in the Onagracese (Ueb. die Bliithenbildung der 
Onagraceen, Schenk's Mittheilungen, II. 1875), the placenta is an independent organ, probably a 
phyllome, a view which was held by Treviranus (Physiologie, II. 1838). 
Now with regard to the ovule. Schleiden, Braun, and most of the older botanists regarded 
the ovule as being a bud, but many regarded it as a leaf or part of a leaf (for the early history of the 
subject see Braun, Polyembryonie und Keimung von Ccelebogyne, i860), a view which, as stated 
above in the text, has been more recently revived by Cramer ; this view has been further developed 
by Celakovsky (Ueb. die morphol. Bedeutung der Samenknospen, Flora, 1874; Discussion 
ueber das Eichen, Bot. Zeitg. 1875, and Vergrünungsgeschichte der Eichen von Alliaria officinalis, 
ibid. 1875, und von Trifolium repens, ibid. 1877), and so far modified that, according to him, the 
