276 Chronicles of Science. [April, 



the flower in Mentzelia aurea. He had been able to verify almost all 

 the details given by Payer in his Organogenie as to the same genus. 

 Dr. Dickson called attention to an important point to which Payer 

 has not adverted — viz. the time at which the three carpellary jsrocesses 

 make their appearance. He finds that the carpels are developed at a 

 very early period. They are distinctly to be seen when only the 

 stamens of the first three degrees have appeared, and are probably 

 developed about the same time as the stamens of the second degree. 

 The carpels are thus developed long before the great mass of the 

 very numerous stamens. 



This fact Dr. Dickson considers quite irreconcilable with Payer's 

 idea that the andrcecium in Mentzelia and its allies consists of a 

 plurality of whorls, in which respect Payer holds them to differ 

 essentially from Loasa and its allies where the andrcecium consists of 

 a single whorl of five compound stamens. 



The fact that the greater number of the stamens do not make their 

 appearance until after the carpels, taken in connection with the evi- 

 dent grouping of the stamens of the first three or four degrees, leaves, 

 in Dr. Dickson's opinion, no room to doubt that the andrcecium of 

 Mentzelia consists of a single whorl of five confluent staminal groups 

 or compound stamens. The most important difference between these 

 groups and those in Loasa consists in their being centripetally de- 

 veloped, as regards the axis, in the former, a mode of development 

 analogous to that of the compound stamens in the Myrtacese, while 

 in the latter the development is centrifugal, analogous to that in 

 Hypericum, &c. In Mentzelia, as in Loasa, the staminal groups are 

 superposed to the sepals. Although the difference in the evolution of 

 the staminal lobes in the two cases is undoubtedly an important one, 

 Dr. Dickson thinks that botanists would hardly be justified in 

 separating the Mentzeliae and Loaseae into distinct orders, as has 

 been done by Payer in his Leqons sur les families naturelles. The 

 analogy between the two groups in all respects excepting the staminal 

 evolution, is so remarkably close, that it cannot but be satisfactory to 

 be able to retain the old order Loasaceas intact. 



In speaking of climbing plants at a late meeting of the Linnean 

 Society, Mr. Darwin says : — " The perfection of the organization of 

 plants is forced on our minds by the study of the many kinds that 

 climb. Let us look at one of the more highly-organized tendril- 

 bearing climbers. It first places its tendrils ready for action, as a 

 polyp places its tentacles. If the tendril be displaced, it is acted on 

 by the force of gravity and rights itself. It is acted on by light, and 

 bends towards or from it, or disregards it, whichever may be most 

 advantageous. During several days, the tendril or internodes, or 

 both, spontaneously revolve with a steady motion. The tendril 

 strikes some object, and quickly curls round and firmly grasps it. 

 In the course of some hours, it contracts itself into a spire, dragging 

 up the stem, and forming an excellent spring. All movements now 

 cease. By growth, the tissues soon become wonderfully strong and 

 durable. The tendril has now done its work, and done it in an ad- 

 mirable manner." 



