496 



HUTCHINSON'S POPULAR BOTANY 



FIG. 625. POPLAR (Populus). 



Part of fruiting catkin discharging its seeds, which 



support a tuft of fine silky hairs which assist 



dispersion. 



the axis of the style after its five-partite 

 outer layer (to the base of which the car- 

 pels are attached) has ceased to grow. A 

 state of great tension is thus produced, 

 and when the splitting takes place the 

 carpels are actually pulled out by the 

 roots, whereupon they roll up upon them- 

 selves as though frightened at what 

 they have done. In -the Marsh-cranesbill 

 (G. palustre) the contraction is so violent 

 that the seeds are hurled to a considerable 

 distance. 



A minute description of the external 

 forms and subsidiary appendages of the seeds of plants hardly falls within 

 the scope of the present work. The testa, or outer integument, may be 



smooth, as in the Bitter Cucumber (Ci- 

 trullus colocynthis] ; reticulated, as in 

 Larkspur (Delphinium, fig. 593) ; papillose, 

 as in thf Corn-cockle {Lychnis githago, 

 fig. 626) ; ridged, as in the Rangoon 

 Creeper (Quisqualis indica, fig. 629); or 

 woolly, as in the Brazilian climbing shrub, 

 Trigonia villosa (fig. 633). The seed of 

 Leptodermis lanceolata (fig. 632), a Bengal- 

 ese evergreen shrub, is enclosed in a re- 

 ticulated sac of endocarp ; while others 

 are more or less enveloped in a remark- 

 able appendage known as the arillus, 

 which springs from their point of attach- 

 ment to the placenta. The arillus is split into long silky hairs in the 



Willow (Salix) ; in the Nutmeg-tree (Myris- 

 tica moschata] it consists of a dry flocculent 

 coat (from which the mace of commerce is 

 obtained) ; and in the Common Yew (Taxus 

 baccata] it is succulent. The manner in 

 which the aril of the Yew grows up 

 around the seed is shown in fig. 631. 

 Winged seeds are common in the G-ynino- 

 sperms, and are borne on scales, which 

 are hence called ovuliferous scales. The 

 Scots Pine (Pinus sylvestris) furnishes a 

 ready example. On a dry breezy day the 

 cones open with a crackling sound and 

 set free the seeds, which fly twirling 



FIG. 626. CORN- 

 COCKLE (Lychnis 

 githago). 



Tapillose seed. 



FIG. 627. 

 L ARKSPUR 

 (Delphinium). 



A reticulated seed. 



FIG. 628. SYCAMORE (Acer pseudo- 



platenus). 

 Samaras or bipartite schizocarp. 



