STAMENS. 89 



with. They occur, however, in certain species of Omithogalum (e.g. Ornithogalum 

 nutans and chloranthum), in Allium rotundum and sphcerocephalum, and in the 

 Monkshood (Aconitum). Occasionally such staminal stipules are modified as honey- 

 secreting glands at the base of the stamen, e.g. Doryphora {ef. figs. 214 ^^ and 214 ^°). 



It sometimes happens in monstrous flowers that the stamens are transformed 

 into carpels, or we may find here and there an isolated stamen, which is partly so 

 modified and partly still poUiniferous. In such monstrosities it usually happens 

 that it is the upper part which forms pollen, and the lower part which produces 

 ovules (cf. figs. 213 =• and 213 ^). From this and other facts it has been inferred that 

 the ovary corresponds really to the sheaths, the style to the petioles, and the stigma 

 to the laminae of the floral-leaves concerned. The monstrous flower of a Saxifrage 

 (figs. 213" and 213^^) shows that anthers and ovules can be produced from the 

 same part of the leaf -stalk. This flower (213^^) produces at the periphery five 

 sepals and five narrow, green petals; in the centre two carpels (shaded dark in fig. 

 213 ^^) as in normal Saxifrage flowers. Between the petals and carpels, i.e. where the 

 stamens are usually found, there are ten structures which, whilst resembling both 

 carpels and stamens to some extent, remind one forcibly of the excavated leaf- 

 rachis of so many of the Pitcher Plants (cf. vol. i. pp. 125-133.) One of these 

 is represented in fig. 213-'^. Its free extremity consists of an irregularly serrated 

 scale, which may be compared either to a stigma or to the continuation of an 

 anther, and may be regarded as the metamorphosed lamina. The excavated portion 

 below may be regarded as the petiole. In its cavity are four rows of yellow 

 protuberances, which might at first sight be taken for ovules. Closer investigation 

 shows, however, that they contain pollen-mother-cells, each inclosing four pollen- 

 grains. Here, then, we find the petiole consisting partly of carpel and partly of 

 anthers, from which it may be concluded that that portion of the carpel which 

 produces ovules corresponds entirely in position to the pollen-producing tissue. 



The parts of the anther which produce Pollen in special chambers are known 

 as Pollen-sacs, the tissue which binds these together as the connective. The 

 connective is a direct continuation of the filament, and, like this, is penetrated 

 by a vascular bundle. The pollen-sacs may be arranged like niches around the 

 columnar connectives, which itself terminates in a sort of little shield, as in the 

 Yew Tree (cf. fig. 234 ^), or they may be situated symmetrically right and left of it. 

 In the latter case the pollen-sacs may lie at the edge of the connective in one 

 place, as in the Juniper (figs. 214^^ and 214^*), or they may be in pairs, i.e. two 

 pollen-sacs to the right and two to the left of the connective (fig. 214 ^). This 

 latter form is by far the most frequent, and occurs in certainly 90 per cent of 

 all Phanerogams. It must be pointed out that the two pollen-sacs of each pair 

 are separated from one another by a partition-wall only in the young anther. 

 This disappears later on, and in the mature anther one finds, instead of four, only 

 two sacs filled with pollen. Sometimes all four pollen-sacs run together in this 

 way, by the breaking down of the parti-walls, as in Sundew (Drosera), Moschatel 

 (Adoxa), Monotropa, and especially in Globularia (cf. figs. 216^'' and 216^). In 



