92 STAMENS. 



four cavities remain distinct, a curious aperture is formed above each of them, 

 as, for instance, in Theobroma Cacao (figs. 216^^ and 216^°). When, however, 

 the aforesaid fusion takes place (e.g. Calla palustris, figs. 216 ^* and 216 ^^), two 

 openings only are formed. The anthers of Olobularia have a very small 

 punctiform connective and four pollen-sacs joined into an ellipsoidal body. After 

 the disappearance of the parti-walls, leaving a single cavity occupied by pollen, 

 a gaping, transverse slit arises, so that the anther is transformed into an open 

 vessel (cf. figs. 216^'' and 216^). After the removal of the pollen the remains 

 of the original parti-walls can be distinguished as two intersecting ridges. 

 Similarly in the Butterwort (Pinguicula, fig. 216^^) and in the majority of 

 so-called one-celled anthers. In many Labiates, in which the anthers of adjacent 

 stamens are in contact, and to some extent united together (syngenesious), the 

 openings of the pollen-sacs in each anther unite, with the result that a pair of 

 somewhat sinuous niches are presented, borne on the two curved filaments (cf. 

 figs. 216 22 and 216 23). 



Dehiscence is accomplished sometimes by the formation of holes or pores, 

 sometimes by slits. Of anthers with porous dehiscence, the greatest variety is 

 exhibited by the Heath tribe and Pyrolaeese. In the anthers of the Bilberry, 

 Bog Vaccinium, Cowberry, and Cranberry (Vaccinium Myrtillus, uliginosum, 

 Vitis-idoea, Oxycoccos), as also in Winter-green (Pyrola), the pouch-like pollen-sacs 

 are drawn out into shorter or longer tubes, each of these tubes opening at its 

 extremity by small circular pores (cf. figs. 216 ^'^^-^2, i4^_ g^^ much more frequent 

 is a dehiscence by means of slits. These are either longitudinal or transverse, 

 or they may be sinuous or semicircular. When they are semicircular a valve 

 or trap-door is cut out of the anther- wall. 



At its first formation the slit resembles one cut by a sharp knife (cf. fig. 216 ^). 

 In a number of cases the margins of the slit remain together, so that the aperture 

 retains the form of a narrow crack; more frequently, however, the slit gapes, 

 its margins roll up outwards or are folded back like a lid or folding-door. The 

 longitudinal slits reach from end to end of the pollen-sacs (fig. 216^), or they 

 may take the form of short gaping clefts near the free extremity of the 

 anther. In the latter case (several examples of which are represented in figs. 

 2ig 2, 3, 6, 7, 9, 10, 13, 16, 16^^ ^j^g g^g ygry much resemble pores, from which they can 

 only be distinguished in some cases by their mode of development. Occasionally 

 the short, gaping clefts of adjacent anther-halves unite into a single opening, 

 with a heart-shaped or rhomboidal outline, by which the whole of the pollen 

 of both anther-halves escapes (examples are Cyclamen and Ramondia, figs. 216 * 

 and 216^). Transverse slits are met with most frequently in the stamens of 

 Euphorbiacese, Cyclanthaceffi; also in a few RosaceaB (Alchemilla and Sibhaldia, 

 figs. 216" and 216^^), in the Golden Saxifrage and Moschatel (Ghrysosplenium 

 and Adoxa), in Olobularia, Malva, and others. On the whole, however, this 

 method of dehiscence is rare. Of still rarer occurrence is that form of dehiscence 

 in which semicircular slits arise in the anther-wall, producing valves or trap- 



