ANGIOSPERMS. 



353 



of foliage-leaves a little way beneath the flower, and this in the allied plant Eranthis 

 hy emalis becomes a kind of epicalyx. The epicalyx of the small flowers of the 

 Dipsaceae is particularly interesting : each flower within the crowded inflorescence 

 is surrounded by a membranous sac, which forms an epicalyx. If, when the 

 perianth and sporophylls of the flower are already formed, a growth takes place 

 from the peduncle beneath the flower, at first as an annular swelling which after- 

 wards developes into the form of a cup and produces scaly or spinous emergences, 

 the structure thus formed is called a cupule; of such a kind is the cup in the 

 acorn of some species of Quercus l ; in this case the cupule only surrounds a single 

 flower, but in Castanea and Fagus it envelopes a small inflorescence, and this spiny 

 cupule afterwards opens by valves from above 

 downwards to release the ripened fruits. If 

 an inflorescence is surrounded with a pecu- 

 liarly developed whorl or with a rosette of 

 leaves, as in the Umbelliferae and Com- 

 positae, this envelope is termed an in- 

 volucre; if a single sheath-like leaf enve- 

 lopes an inflorescence belonging to its own 

 axis, it is called a spathe. Both involucre 

 and spathe may assume a petaloid structure; 

 the former, for instance, in Cornus florida, 

 the latter in many Aroids. 



The androecium is the collective name 

 for all the male sporophylls of a single 



FIG. 273. Longitudinal section of the flower of Lychnis 



flower : each One Of them iS Called a Stamen, flos-y<rvis; y the elongated portion of the axis between calyx 



and corolla, x ligule of the petals (corona). 



and consists of the anther and of fat filament 



on which it is placed ; the filament is usually filiform, but sometimes broad and 

 leaf-like. The anther is formed of two equal longitudinal lobes placed on the upper 

 part of the filament right and left of its median line ; the part of the filament which 

 bears the anther-lobes is distinguished as the connective. 



The position of the stamens on the floral axis or torus in all hermaphrodite and 

 in most purely male flowers is unquestionably lateral. From this lateral position of 

 the stamens, from their exogenous origin from the primary meristem next the 

 growing point of the floral axis, from their acropetal development and their frequent 

 monstrosities in which they assume more or less the character of floral or even of 

 foliage-leaves, they must be regarded in the morphological sense as foliar structures, 

 and may be suitably termed staminal leaves. The lateral position is liable to 

 exception in a variety of cases. In Naias the vegetative cone of the male floral axis 

 becomes a quadrilocular anther 2 by the formation of pollen-mother-cells in four 

 longitudinal peripheral strips of its tissue, and a similar arrangement occurs in 

 Casuarina 3 and in the unbranched stamens of Typha, In Cydanlhera also the 



1 On its development, see Hofmeister, Allg. Morphologic, p. 495. 



2 Magnus, Beitr. z. Morphol. d. Gattung Naias, Berlin, 1870. See also Bot. Ztg. 1869, p. 771. 



3 Kaufmann, Ueber d. mannl. Bluthe von Casuarina (Bulletin de la soc. imp. d. sc. nat. de 

 Moscou, 1868). 



[2] A a 



