LIFE-HISTORY AND PHYSIOLOGY. 13 



the variable colour of the stigmata, is constant; the only exception being the 

 occurrence occasionally of dark chocolate tissue near the base. In C. hyemalis var. 

 Foxii (Plate XLIII, fig. 9), the tissue of the entire anther is chocolate instead of 

 orange; and in C. Crewei (Plate LX, fig. 6) this is a constant specific character. 

 The pollen grains of C. Crewei and C. Foxii are orange; in all the white anthered 

 species, the pollen grains are also white. The anthers vary considerably in their 

 size, and in their length relative to that of the filament in different species; but 

 within each species the size is very constant. The only marked departure in form, 

 from the usual oblong, slightly spreading anther, occurs in C. aureus (Plate LV, 

 n &- 6-7), in which the anthers are suddenly divergent, and taper from the base to 

 the summit. 



The pollen grains (Plate B, fig. 2) vary much in size. In nearly the whole of the 

 spacies they are regular spheres, of from one four hundredth to one two hundredth 

 of an inch in diameter; in the majority of species they are about one three hun- 

 dredth of an inch (0.0008 Metre) in diameter. Within each species the size of the 

 grains is remarkably constant, excepting only in C. sativus, and the allied species, in 

 which the grains are variable in size, and also of irregular outline. In the sterile 

 garden forms of C. aureus (Plate LV b, fig. 1. e.) the effete pollen grains are much 

 reduced and variable in size, and are of irregular outline. In about half the 

 species the grains are papillose, and in the remainder, glabrous. In the grains of 

 C. aureus and its allied species, Mohl was the first to notice the presence of a 

 sinuous, or spiral superficial marking; it is also present in C. carpetanus, and one or 

 two other species. Mr. Carruthers, from whose drawing Plate B, fig. 2, is copied, 

 has ascertained that these markings are slight channeldike depressions, due to the 

 partial thinning of the outer membrane or sack. The pollen grains become very 



Fig. 9. 



quickly distorted in form on their application to the stigma, and previous to the 

 emission of the pollen tube become fusiform. Professor Martin Duncan has pointed 

 out to me the pollen tubes (Fig. 9) have cross dissepiments at irregular intervals, 

 and that molecular movement and cyclosis are to be seen in the tubes amongst 



the granular contents. 



