MORPHOLOGY OF ANGiOSPERAlS. 155 



as in the mustards, when they are said to be accumuent or con- 

 duplicate, or they he so that the back of one is against the hypo- 

 cotyl, as in Lcpidiuiii, which position is known as incumbent. 



Externally, the seed-coats vary considerably ; they mav be 

 nearly smooth, as in ricinus ; finely pitted, as in the mustards ; 

 prominently reticulate, as in staphisagria ; hairy, as in cotton (Fig. 

 166) and strophanthus (Fig. 185), or winged, as in the seeds of 

 the catalpa. There are also a number of other appendages, these 

 having received special names : the wart-like development at the 

 micropyle or hilum of some seeds, as in castor-bean and violet, is 

 known as the caruncle; in the case of sanguinaria, a wing-like 

 development extends along the raphe, and this is known as the 

 STROPHIOLE ; in some cases the appendage may completely en- 

 velop the seed, when it is termed an arillus ; when such an 

 envelope arises at or near the micropyle of the seed, as the mace 

 in nutmeg, it is known as a " false arillus," or arillode. 



Seed Dispersal. Seeds and fruits are distributed in various 

 ways, and so are often found growing in localities far from their 

 native habitat. In some instances seeds are adapted for distri- 

 bution b}' the wind, being winged, as in Pauloivnia, Catalpa and 

 Bignonia, or plumed and awned, as in Strophanthus (Fig. 185) ; 

 Asclcpias and Apocynum (Fig. 201). As examples of fruits hav- 

 ing special parts which aid in their distribution may be mentioned 

 the akene of Arnica which is provided with a pappus (Fig. 241), 

 the bladder-like pericarp of Chenopodium, the winged fruit or 

 samara of maple. The hooked or barbed appendages on some 

 fruits serve to attach them to animals and thus they may be 

 widely distributed, as in the burdock and Spanish needles 

 (Bidcns bipinnata). In still other cases fruits may be carried 

 long distances by water currents, or even by ocean currents, as 

 those of the Double-cocoanut palm {Lodo'icca Seychellarum), 

 which while native of the Seychelles Islands is now found on 

 many of the islands in the Pacific and Indian Oceans. It may 

 also be mentioned in this connection that a number of fruits, as 

 the garden balsam, castor-oil plant, violets (pansy, etc.), Wistaria, 

 etc., are elastically dehiscent and discharge the seeds with con- 

 siderable force. 



