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SCIENCE-GOSSIP. 



distances. The common campion (Lychnis dioica) 

 is an interesting case in point, and is sufficiently 

 well known. Apropos to these monosexual plants 

 a story is told by Jussieu, the French botanist. He 

 had two female turpentine trees (Pistacia terebinthus) 

 which annually blossomed, but bore no fruit. One 

 year, however, the savant was surprised to discover 

 fruit, and as there were no male plants in the 

 neighbourhood to account for the anomaly, he 

 enquired on every side, and was ultimately in- 

 formed that a male Pistacia had flourished in a 

 nursery at Luxembourg, nearly two hundred miles 

 distant. Facts such as these are well known to 

 every botanist. 



What guides the pollen in the air, and prevents 

 its straying when so many different routes offer — ■ 

 when the atmospheric currents could transport it 

 in every direction ? What guides, may be repeated, 

 that impalpable powder in the immense ocean of 

 air, and brings it so surely to its destined end ? 

 Pollen strays in water no more than in air. Aquatic 

 plants in this respect are full of interest. The 

 water crowfoot (Ranunculus fiuviatilis) generally 

 expands its flowers out of the water, but it not 

 infrequently happens that the flower stalk is too 

 short to reach the surface, and in that case the 

 flower-head gradually swells without bursting. 

 This improvised sac contains a gas which acts as a 

 buoy and keeps the flower-head perpendicular to 

 the surface, so that its pollen can neither be lost 

 nor altered by contact with the water, and ferti- 

 lization is carried on without difficulty. I was 

 enabled to personally observe these interesting facts 

 on the Nith, near Dumfries, some months ago. 



In many of the continental rivers is found a 

 plant, neither pretty nor sweet-smelling, but 

 which nevertheless has been long held in admira- 

 tion by botanists. This is the spiral Valisneria. 

 This plant, in botanical nomenclature, is monoe- 

 cious : it bears on the same plant, but on different 

 stems, male and female flowers. The male flowers 

 are on short, straight stems, and the female on 

 a stalk which is a curiously-developed spiral. 

 When the time of fertilization arrives, the male 

 flower, enclosed in a sac and on the point of 

 bursting, is detached from the stem and rises to the 

 surface. The female stem at once unwinds itself 

 and also rises to the surface. Arrived there the 

 male flower bursts, and scatters its pollen, which 

 is received by the pistil. This interesting per- 

 formance over, the female spiral stem resumes its 

 normal position in the bosom of the water. 



Many stories have been told about the sensitive 

 plant. Some who claim no mean eminence in our 

 science ascribe to it an indefinable sort of sensi- 

 bility. But all speculation aside, the facts are : the 

 leaf is compound, and the leaflets are arranged sym- 

 metrically along both sides of the petiole, like the 

 barbs of a feather. If a single bag is touched the 



impression is communicated to all, and in pairs 

 they embrace the stem to its full length, each pair 

 overlapping the other. Thus the physiognomy 

 of the plant is entirely changed, the drooping 

 leaflets and stem give it a withered appearance. 

 After a few minutes it revives and the plant again 

 appears normal. The experiment may be carried 

 on indefinitely, and if the plant is healthy and 

 vigorous and the temperature slightly above 

 normal the phenomenon is more marked and 

 rapid. 



The marks of fatality peculiar to instinct are 

 said to be very evident here, so much so that 

 many investigators, particularly on the Continent, 

 believe these especial plants to possess a vegetable 

 consciousness, whatever that may mean. Whether 

 or no, judgment must be suspended. 



If we examine the sensitive plant, at the base of 

 the petiole, just where the leaf is attached to the 

 stem, a small node is found called the motor node, 

 because on it depend the peculiar movements of 

 the plant. It is the condition of this node that 

 determines the rigidity and flaccidity of the leaf. 

 The explanation is that one of the functions of the 

 plant is to develop glucose, which accumulates 

 in the nodes. There it absorbs moisture and the 

 stem becomes rigid ; but the glucose gradually 

 decomposes, finally disappearing, and with it the 

 accumulated water; then the leaflets become flaccid. 

 The glucose is the cause of the movements, and 

 this substance owes its existence to sunlight. 

 Under the influence of sunlight it is formed, and 

 in its absence is destroyed. During the day it 

 accumulates gradually in the nodes, there is there- 

 fore a concentration of moisture, a determination 

 of moisture to that part, and a progressive rigidity 

 of the stem. This operation is gradual and con- 

 tinuous. Then follows a series of inverted pheno- 

 mena at regular and periodical intervals. Thus 

 that marvellous instinct, that apparent sensibility, 

 is transformed into chemical action which deter- 

 mines a mechanical act. 



The rotation of the common sunflower is due 

 to a similar cause. The' capitulum inclined at a 

 constant angle follows the sun in its march. This 

 phenomenon proceeds from a difference of energy 

 between the two opposite surfaces of the stem. 

 The one surface is constantly exposed to the sun, 

 while the other is not. In the one case glucose 

 is formed, and in the other it is decomposed From 

 this results the movements which have gained the 

 flower its name. As the sun proceeds in his march 

 over the heavens, the different parts of the surface 

 are successively exposed to his rays, and so the 

 movement is propagated round the stem. 



Phenomena such as these have, in reflective and 

 intelligent minds, raised the question whether 

 plants are capable of sensation, whether they are 

 conscious of pain, whether vitality can be destroyed 



