ure as the seeds are in want of for absorption, an atmosphere 

 which is almost completely saturated with vapour. This is 

 also applicable to the other periods of vegetation (as is shown 

 by the vegetation in the moist tropical forests. Rep.}. And 

 it thence follows, that in the hot-houses of our gardens the 

 influence of vapour on vegetables should be employed to a 

 far greater extent than has hitherto been the case. 



The Feuilleton du Temps, 18 Avril 1837, contains a more 

 detailed communication of the memoir by MM. Edwards and 

 Collin, from which I will mention some of the results obtained. 

 In the open atmosphere, even when it is very moist, the seeds 

 of plants are said not to germinate. I have, however, only in 

 last year's Report mentioned exceptions to this rule. The 

 seeds of grain germinate in an atmosphere saturated with 

 moisture ; under water they require eight times the length of 

 time. With a simultaneous action of water and vapour, the 

 seeds germinate earlier when the atmosphere is saturated with 

 moisture. 



Morphology. 



From the great number of memoirs which appeared in the 

 course of 1837 treating of the morphology of plants, I shall 

 first select that of M. von Martius*, as the subject is there 

 treated in a more general way. 



First Lecture. The plant, observes von Martius, is an or- 

 ganized body expanded between heaven and earth, free above, 

 but below fettered in the bands of the earthly. The plant 

 lengthens upwards and downwards, and differs in this twofold 

 growth, the descending and the ascending, so completely, that 

 the appearance of its two large systems is accompanied with and 

 incloses totally distinct formations. The root is essentially 

 the simple uniform portion (shut up as it were within itself) 

 of the plant. It constantly persists in its downward direction ; 

 it increases in length and in breadth ; can ramify by division ; 

 but neither is it as a whole, nor are its individual parts, ca- 

 pable of transformation. The ascending axis of the plant is its 

 solar and aerial system ; it is diametrically opposed to the 



* Die Metamorphose der Pflanzen. Four lectures. Reden und Vortrage, 

 &c., p. 111-223. 



