264 PHYSIOLOGICAL BOTANY. 



expressions should be selected, instead of such indistinct 

 and incorrect ones as uni- and bin -axial, because these 

 are very obscure. In these investigations Wydler has 

 especially endeavoured to explain the remarkable struc- 

 ture of the Solanacese. It is so marked that the Natural 

 Order is recognised by it, however the same occurs in 

 other Natural Orders and individual genera, for instance, 

 in the Boraginaceae, Phytolacca, and others. 



ROOT. TUBERS. PRICKLES. TENDRILS. GLANDS. STOMATA. 



On the Tendency of Roots to strike into the Earth (but 

 really into mercury only). By PAYER. Compt. rend., 

 1844, i, 993. In the year 1829, says the author, Pinot 

 remarked that some seeds of Latliyrm odoratus, which 

 he had caused to germinate upon mercury, forced their 

 radicles into it. This penetration was afterwards con- 

 sidered to arise merely from the weight of the seed; 

 others did not observe any penetration ; and De Candolle 

 regarded the penetration as arising from the stiffness of 

 the root. Payer then made some experiments upon the 

 point, and found that the radicles of Polygonum Fago- 

 pyrum, although they are stiff and thick enough, remained 

 on the surface, whilst, on the other hand, the much more 

 delicate roots of Lepidium sativum penetrated to a con- 

 siderable depth. Nor does the weight at all contribute 

 to the effect. If the root be withdrawn from the mercury, 

 it does not again penetrate the metal, but it sometimes 

 shoots further, and then the new portion does so. Light 

 and heat increase its power of penetration. The author 

 thinks that the power possessed by the roots of penetrating 

 the earth arises from their power of avoiding light, and 

 seeking for proper soil. This is explaining something 

 that is unknown by something else which is still more 

 unknown. We have only given an extract from the 

 memoir. 



The results, only, of a memoir, by Durand, upon the 



