26 Elementary Work in Botany. 



as represented at d. The mimic caulicle really a tube 

 formed by the united stems (petioles) of the thick cotyledons, 

 and only tipped by the caulicle penetrates the ground to a 

 depth, usually, of four or five inches. The plumule mean- 

 while, as shown in/", remains dormant in the bottom of the 

 tubular sprout. When the petiole growth ceases, the cauli- 

 cle grows rapidly by absorbing the nourishment stored in 

 the cotyledons, and becomes thick like a radish. Meanwhile 

 the plumule begins its upward growth, splitting the petioles 

 apart, and usually escaping from between them, as shown 

 in the figure below c. In this wonderful way the plumule 

 bud is deeply planted together with nourishment (stored in 

 the caulicle), which, if necessary, can be used to aid its 

 first growth. The reason for this curious behavior is 

 obvious, when we know that ground squirrels are fond of 

 these seeds, and that a severe frost will kill the young 

 plant. If the seeds wait till warm weather to sprout, hun- 

 gry rodents may find them; if they germinate early, and 

 in the manner of other seeds, Jack Frost may nip them.* 



* Dr. Asa Gray, who first experimented with these seeds, found them to grow 

 as represented at a, in the figure (reduced to one-fourth natural dimensions from 

 P'ig. 43, Botanical Text-book, edition of 1879). Evidently on account of some 

 obstruction, probably the bottom of a small pot, the seeds were elevated two or 

 three inches above the surface of the soil (the dotted line S represents the surface 

 of the ground for Figs, a, <5>, and c ). My experiments with seeds planted in shallow 

 boxes gave very different results shown at &, which is a reduced copy of Fig. 14 

 of second edition of the Popular California Flora. The plants came up about 

 four inches from where the seeds were planted, the plumule being pushed later- 

 ally that distance by the elongation of the cotyledon petioles. Such inexplicable 

 behavior stimulated to further observation, which resulted in the discovery that 

 naturally planted seeds, unhampered by boxes or pots, usually grow as repre- 

 sented at c and d. In one instance a sprout measured seven inches from the 

 plumule to the cotyledons. The hairs at e probably help the sprout to penetrate 

 the soil by fastening on to the surface crust. Curiously enough, growing: sprouts 

 underground frequently avoid obstacles without touching them. [See Darwin's 

 Movements of Plants, p. 80.] 



