PROTECTION OF RIPENING SEEDS AGAINST ANIMALS. 



443 



able morsels for animals. A less common condition, and one deserving of special 

 mention, occurs in several Mimosas belonging to the immediate alliance of the 

 Sensitive Plant (e.g. Mimosa piidica, M. polycarpa, M. hispidula); of these the 

 last-named may serve as type (see fig. 339^). The pods here are densely crowded 

 together, and their dorsal and ventral sutures form a strong framework bearing a 

 double row of short spines. These spines hinder all animals from interfering with 



Fiir. 337.— Coniferous Fruits and Seeds. 



I Branch of the Larch (Larix Europtea) with ripe cone. ^ Branch of Pinus serotina with ripe cone, s Female flower 

 of the Cypress. * Longitudinal section of the same, s Ripe cone of the Cypress {Cupressits sempervirens). s Single carpel 

 of the Cypress witli numerous ovules. 7 Branch of Gingko bUoba with unripe fruit, h 2, 5, r natural size. The other 

 figures enlarged. 



the fruits. As the seeds ripen, the valves fall awaj" from their spiny framework, 

 and are, with their contained seeds, dispersed by the wind. As a rule, the valves 

 break up at this time into one-seeded segments (fig. 339^), and being very light in 

 proportion to their area, are carried considerable distances. 



In the instances just enumerated the protection is provided only up to the time 

 that the seeds are ripe. With the severance of the seeds from the parent plant the 

 protective function of the spines is at an end. The spinose investment as a rule 

 remains upon the plant, and only rarely, as in the winged fruit of Centrolobiuvi 

 rohustum (see fig. 339^), does the thorny ovary wall (pericarp) become detached 

 with its contained seed. Under these circumstances the spines may play a further 



