334 AJmUAL OF SCIENTIFIC DISCOVERT. 



Temperature at which Plants Oerminate. — According to Alph. De 

 Caiulolle, in the "Proceedings of tlie Societe llelvetique dcs Sci. 

 N:it.," 18G6, white mustard seed will germinate below 3:^° F. ; 

 TrifoUum repens at a little above 42° F. ; Indian corn at 48° F., 

 but not below 42° F. ; sesamum at 55.4° F. ; melon seed at G3° F. 

 Seeds will not germinate above certain temperatures, varying with 

 their species and the amount of moisture present; thustlie greater 

 jjart of some T. repens seed did not germinate above 83° F. Tims, 

 seeds only germinate between certain limits of temperature, and 

 those which can only do so within narrow limits are least able to 

 extend themselves geogniphically. 



The Change of Leaves. — Tiie cause of the beautiful tints which 

 our foliage assumes diu-ing the autumnal months has long been 

 a sulycct of investigation, and many are the hypotheses that have 

 been put forth in explanation. 



hi. Fremy, who has devoted considerable attention to this sub- 

 ject, stated, as the result of a series of experiments, that he had 

 succeeded in resolving the green coloring matter of the leaf 

 {chlorophyU) into two com])onents ; one, a yellowish substance, he 

 called ])hijlluxanthin, the other, a blue matter, for which he ])ro- 

 posed the name phi/lloci/anin. By considering the blue as more 

 evanescent, the dillerent shades of yellow leaves might be pro- 

 duced. 



These views were very generally accepted, till recently Fremy 

 has again appeared, essentially retracting his oi'iginal views. He 

 now gives, as the result of subsequent experiments, the new sup- 

 position that cldorophijll is a simple green coloring matter very 

 unfixed, being influenced by vegetation, thus passing through 

 varied modifications. 



M. Carey Lea, of Philadelphia, has lately advanced a theory in 

 which he considers light as the primary cause, producing photo- 

 graphic changes of color. 



Dm-ing the healthy state of the leaf, vitality counteracts this 

 influence, but as the fall approaches the frost l^egins its work ; 

 the petioles dry up, the leaf graduallj' loses its firm hold upon the 

 branch, then the action of light, no longer held in check by the 

 vital principle, predominates, the leaf falls away, but in fading 

 acquires those brilliant hues that variegate our forests. — Scientific 

 American. 



The Giant Radish of Java. — The Raphanus caudatus, the giant 

 radish of Java, where it is known as INIougri, has been recently 

 introduced into England, and is found to thrive extremely well in 

 common gardens, the seeds germinating easily, and the plants 

 producing a profusion of blossom in about eight weeks, the j^lant 

 often making a growth of five or six inches in twenty-four hours. 

 The root is not eaten, only the pods, which often attain a length 

 of three feet. The plants should be tied ujn-ight, as they produce 

 from fifteen to twenty pods each, growing in fantastic and irreg- 

 ular shapes. Eaten raw, the Raphanus has much the flavor of the 

 most delicate radish, and is a great addition to a salad. When 

 boiled, it should be served up on a toast like asparagus, which it 

 resembles in flavor, but with a dash of the taste of early green 

 peas added. The pods also make a good pickle. 



