376 



FOURTH GROUP. SEED-PLANTS. 



Among superior ovaries with axial^ placentation those ofNaias* and the Piperaceae 

 specially deserve attention, in which the very simple female flower consists merely 

 of a small lateral shoot transformed into an ovary with a central ovule. The apex 

 of this shoot is itself said to become the terminal nucellus of the ovule, round which 



FIG. 307. Development of the ovary of Phlomis putigens, one ol the Labiatae ; age according to the order of the 

 numerals / to VII ; V is a longitudinal section, the rest are transverse sections. A a mature gynaeceum seen from 

 without. B a similar one in longitudinal section. The lines o and in B answer respectively to the transverse sections 

 VII and VI \pl denotes the placenta, x the spurious dissepiments, f compartments of the ovary, sk the ovule, c the wall 

 of the carpel, t the disc, n the stigma, g the style, m to m the median plane of the carpels. 



an annular wall grows up from beneath and overtopping it at length closes over 

 it, and forms the wall of the ovary; in Typha? a single style only with a stigma rises 

 above the ovary, and the latter is therefore considered to be formed of a single 

 carpel, which rises up from the floral axis as an annular wall ; but in the Piperaceae 

 the stigma which is sessile on the apex of the ovary often has several lobes or is 

 placed obliquely; this, like the two to four styles on the ovary of Natas, indicates 

 that the ovary is formed not of one but of several carpels, which like the leaf-sheaths 

 of the Equisetaceae are at first an undivided annular growth and afterwards separate 

 into teeth at the upper margin. This view appears the more admissible because 

 in other Angiosperms, in which comparison with allied forms justifies the assumption 

 of a number of coherent carpels, these grow up as an undivided annular wall, which 

 developes into the ovary and above it into the style and stigma, as in the Primulaceae 

 (Fig. 309). In the Polygonaceae on the contrary, the ovary, which is there also 

 eventually a unilocular chamber enclosing the central ovule, is seen to be formed 



1 [Axial placentation (that is, placentas upon the floral axis) as distinct from carpellary placenta- 

 tion must not be confounded with ' axile ' placentation of many English text-books, which according 

 to the views expressed in this work is a carpellary form.] 



2 Magnus, Zur Morph. d. Gattung Naias (Bot. Ztg. 1869, p. 772). Hanstein u. Schmitz, 

 Ueber Entw. d. Piperaceenbliithen (Bot. Ztg. 1870, p. 38"). Schmitz, Die Bliithenentwickl. d. 

 Piperaceen in Hanstein, Bot. Abhandl. II. Bd., i Heft. 



8 The ovule in this case is not terminal on the floral axis, as has been stated, but grows from 

 the bottom of the carpel. 



