542 PHANEROGAMS. 



But, besides, the morphological homology of the separate parts of the ordinary 

 stamens is not yet altogether determined, more precise investigations into the history 

 of development being still wanting in this direction. Cassini and Roper consider 

 the two anther-lobes as the swollen lateral halves of the lamina of the stamen ; their 

 loculi would therefore in that case be mere excavations in the tissue of the leaf; 

 the pollen-mother-cells become differentiated inside the young tissue of the leaf, 

 According to this view the furrow between the two pollen-sacs of an anther-lobe (see 

 Fig. 357, ZT) would correspond to the margin of the staminal leaf; but this cannot be 

 the case\ at least not always, according to Mohl's observations. When the stamens 

 become transformed into petals (by the so-called ' doubling ' of the flower) as in the 

 Rose, Poppy, Nigella damascena, Sec, it may be observed with certainty that the 

 anterior and posterior loculi do not stand opposite one another, which would be 

 the case if one belonged to the upper, the other to the under side of the staminal 

 leaf; but that both are formed on the upper surface, the anterior loculus nearer the 

 median line of the leaf, the posterior one nearer its margin. It is further observable 

 that in such cases the two pollen-sacs of an anther-lobe do not always stand close to 

 one another, but that they are frequently separated by a tolerably broad piece of the 

 leaf, and that this intermediate piece contracts in the normal state into the par- 

 tition-wall between the two pollen-sacs. The greater stress must be laid on these 

 observations of Mohl, because in Uiem the abnormal development only shows more 

 plainly what can often enough be seen in a horizontal section of the anther and 

 connective of normal stamens, viz. that the pollen-sacs of an anther-lobe evidently 

 belong to one side of the stamen ; it appears, however, that they must in some cases 

 be referred to the under (Fig. 357, C, H), in others to the upper side (Fig. 360, C). 

 The origin of the pollen-mother-celis and the development of the wall of the separate 

 pollen-sacs calls to mind so vividly in all essential features the corresponding pheno- 

 mena in the sporangium of Lycopodiacese and even of Equisetacese, that it may be 



und Gnetaccen, 1872. — Hieronymus, Zur Deutung sogen. axiler Antheren, Bot. Zeit. 1872, and 

 Beitr. z. Kennt. d. Centrolepidaceen, Halle 1873. — Reuther, Beitr. z. Kntwick. d, Bluthe, Bot, Zeilg. 

 1876.- — Engler, Beitr. z. Kennt. der Antherenbildung, Jahrb. f. wiss. Bot. X. 1876. — Celakovsky, 

 Teiatologische Beitiage zur morphol. Deutung des Staubgefa ses, Jahrb. f. wiss. Bot. XI. 1878. 



With reference to Typha, Magnus finds that the apparently axial stamen consists really of three 

 coherent lateral stamens. In Naias, Casuarina and Cyclanthera, the stamen is undoubtedly axial. 

 It would appear, therefore, that stamens are not always phyllomes. It is still possible, however, that 

 they may be phyllomes in these cases. Celakovsky goes so far as to regard the stamen of Naias as 

 a terminal leaf, a quite impossible morphological conception (Flora, 1874). The researches of 

 Hieronymus tend to show that the statement made above on p. 491 may be near the truth, namely, 

 that in these cases the pollen-sacs may be the surviving portions of otherwise abortive staminal leaves. 

 In Brtzula, one of the Centrolepidacese, he finds a single axial stamen ; in Alepyrum and Centrolepii he 

 finds that the stamen is developed from one longitudinal half of the growing-point, and that the other 

 half, the persistent growing-point, is forced on one side by the growth of the stamen, so that the 

 stamen lies in the same straight line as the long axis of the stem. He finds this to be the case also 

 in a Grass, Festuca pseudo-viyvrus ; in the nearly-allied F. geniculata, which usually has three lateral 

 stamens, it sometimes happens that only one stamen is present, and this is then developed in the 

 manner described above. On the other hand, these facts may Ije used to prove that a stamen may be 

 sometimes a caulome and sometimes a phyllome. It must be borne in mind that the ideas of 

 caulome and ph}llome are relative and not absolute.'] 



^ H. V. Mohl, \^ermischte Schriften, p. 42, 



