181 REVIEW. 



way. It is difficult to propagate by slips, woods which are very dense and 

 contain much resin, as the Fir and Oak. 



" These processes tor the propagation of plants are, in many cases prefer- 

 red to multiplying by seed. Propagation by slips or layers always pro- 

 duces the same variety, as that from which the slip is taken, so that we 

 have a plant that produces good fruit by propagation in either of these modes, 

 several mav be raised bearing fruit equally good. The tree is always 

 more speedy in bearing fruit when formed in this way, than when giown 

 from a seed. 



" It is an interesting fact, and which is turned to good account in the 

 cultivation of fruit trees, that, when the tree is raised in this way, the number 

 of seeds iu the fruit is almost always less than when produced from a seed, so 

 that more of the juices and strength of the plant are expended in perfecting 

 this fruit, The Vine when raised from seed, has four seeds in each grape ; 

 but frequently only two when propagated by layers. 



" The Sugar-cane, which is propagated nearly in a similar manner, bears 

 no seed at all, but the other parts of the plant are richly developed. Thus 

 also, the seeds of the plants mentioned before are rarely ripened; and in com- 

 mon Solomon's Seal (Convallaria multiflora), the berries are seldom rip- 

 ened, the plant increasing much by root." 



Outlines of Human Physiology. By Herbert Mayo. 



In lately perusing this new work, we found the following in- 

 teresting account of an experiment to determine why the roots 

 of plants shoot downwards, by the ingenious Mr. Young: — 



" It is impossible not to be struck with the close analogy which holds 

 between the phenomena of the irratibility and movements of the sensitive 

 plants and many of the instinctive motions of animals. The discrimination 

 evinced by plants is a subject no less curious. Climbing plants stretch to- 

 wards objects calculated to support them ; a shrub when growing upon a 

 wall, when it has exhausted the nourishment which its situation afforded, 

 has been known to drop a long root to the soil below. The daisy, in rank 

 grass, bears a flower upon a long stalk ; on a close shaven lawn, its flower is 

 sessile. These and similar instances have been occasionally ascribed to an 

 instinct in plants ; it is much more philosophical to suppose, that the growth 

 of plants is determined by physical impressions alone, such as variations of 

 moisture or temperature, and exposure to or deprivation of light: and that 

 nature, instead of imparting perception to plants as their guiding principles, 

 has attained her purpose by another method, having so framed and endowed 

 the vegetable economy in accordance with the circumstances in which it is 

 placed, that the common accidents of the elements and of the seasons are 

 likely to bring it to perfection. Several remarkable examples go to prove 

 the correctness of the preceding views, out of which it may be proper to 

 adduce the following: it is well known that, in whatever position a seed 

 is laid in the ground, the plumule invariably rises towards the surface 

 of the soil, while the radicle, on the contrary, shoots downwards. Upon the 

 hypothesis that physical impressions determine the growth of plants, we 

 should expect to find that gravitation is in this instance the influential cause, 

 or that the growth of the radicle necessarily follows the direction of a me- 

 chanical force or tendency to motion, while that of the plumule goes against 

 it. Mr. Ivniglit ascertained this solution to be just, by experiments, in which 

 another force was made to supersede, or to co-operate with, that of gravity. 

 Seeds of the garden bean, which had been pieviously soaked in water, were 



