MORPHOLOGY OF ANGIOSPERMS. 155 



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

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

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



Externally, the seed-coats vary considerably; they may 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 <his 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 by the wind, being winged, as in Paulownia, Catalpa and 

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

 Asclepias 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 burdock (Fig. 92) and Spanish needles 

 (Bidens 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'icea 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 gar- 

 den balsam, castor-oil plant, violets (Fig. 93), Wistaria, etc., are 

 elastically dehiscent and discharge the seeds with considerable 

 force. 



