II CHUCIFER^ 85 



and winged, which doubtless helps towards dispersion. 

 Moreover, when wetted the cells at the edges of the 

 wing swell up and ultimately burst, liberating a 

 mucilage, which is useful in fixing the seed to the damp 

 earth. 



COCHLEARIA 



A genus of perennial herbs with small white flowers 

 and inflated pods. There are about twenty-five species 

 in temperate and Arctic regions, chiefly littoral and 

 alpine. Two are British. 



C. officinalis, subsp. danica. — The subglobose silicule 

 is two-celled, with four to six seeds in each cell, and 

 opens by two turgid valves. The small ellipsoid seeds 

 are somewhat compressed laterally, with a rather deep 

 notch at the base. The deep brown seed-coat is covered 

 with large crystalline, truncate, or slightly funnel- 

 shaped tubercles, in lines following the curvature of the 

 seed. "When the seeds are placed in water the truncate 

 tubercles gradually elongate, becoming several times 

 longer than they were in a dry state, and hyaline or 

 transparent, showing striated and filiform thickenings 

 internally ; they also lose their truncate form, becoming 

 obtusely conical. They do not burst, even after having 

 been for some time in water. Many of those lying 

 above the water merely become many times larger than 

 they were previously and dome-shaped, showing a very 

 fine internal striation. Such mucilaginous cells when 

 pushed into surrounding soil must serve to fix the seed 

 efi"ectually during germination, but they may also aid 

 in the dispersal of the seeds. 



C. Armoracia (Horse-radish) has nectaries at the base 

 of the stamens, but in C. officinalis Knuth could find 

 none. The former is, however, visited by a good many 

 insects for the sake of the honey. The plant, which is 

 found on waste ground, is not a native. Its origin is 

 unknown ; it is suggested that it is a cultivated form of 

 a Hungarian species, C macrocarpa. 



