400 PLANTS OF NEW ZEALAND 



Genus Sicyos. 



Annual creeping herbs. Calyx 5-toothed, corolla 5-lobed. Filaments 3 : 5, 

 anthers united. Staminate flowers racemed, pistillate panicled. Fruit small, 

 leathery, 1-seeded. Tendrils branched. (Name from the Greek, signifying a 

 .cucumber.} 



Sicyos austral is (The Southern Sicyos). 



A glabrous herb, with stems 2 ft. -10 ft. long. Leaves 5-7-lobed. Flowers 

 .green, ^ in, across, axillary. Fruit a nut, with barbed spines. Both islands: 

 very rare. Fl. Dec. -March. Found also in the Kermadecs and Norfolk Island. 



This is one of the many climbing plants of New Zealand. 

 Sicyos climbs by tendrils, as also do Clematis and Passiflora. 

 The tendril-bearing plant has a great advantage over other 

 forms of climbers. It can grip hold of smaller projections 

 than can be seized by a twining stem, and can climb up 

 great tree-trunks by this means, when such a stem would 

 fail altogether to ascend. Nature rarely develops a new 

 organ for a new function, but generally modifies an old 

 one to do the work. Thus, we find that tendrils are merely 

 modified leaves or stems, or even roots. In Clematis, it is the 

 petiole that forms the tendril ; in Passiflora tetrandra, and 

 Sicyos, the tendrils are probably modified branches. The 

 twining of a tendril is caused by its outer side growing more 

 rapidly than the inner, and thus producing curvature. The 

 tendrils of Sicyos are unusually sensitive, and, a few minutes 

 after they touch an obstacle, the tips will completely encircle 

 it. The tendency to curve is also communicated to the rest 

 of the tendril, so that it coils up like a corkscrew. Now, as 

 both of its ends are fixed, it is clear that the torsion would 

 soon cause it to snap, if some provision were not made 

 to guard against such an accident. This misfortune is 

 ingeniously prevented, by the reversal of the spiral. One 

 part of the tendril coils from right to left, while the other part 

 is twisted in the opposite direction. A short straight portion 

 unites the two coils. There are several advantages in the 

 reversed spiral. If a tendril is twisted an equal number of 

 times in opposite directions, then there is no strain from the 



