6 3 6 



THE POPULAR SCIENCE MONTHLY. 



those who started with half-developed pow- 

 ers and half-furnished minds. 



Insects and Flowers. In his lecture at 

 Belfast, on " Common Flowers in Relation to 

 Insects," Sir John Lubbock inquired into the 

 causes of flowers closing their petals dur- 

 ing raiu, and of some flowers remaining 

 open for a longer or shorter period than 

 others. The habit of closing the petals 

 during rain is obviously an advantage, since 

 it prevents the honey being spoilt or washed 

 away. Everybody, however, has observed 

 that even in fine weather certain flowers 

 close at particular hours. This habit of 

 going to sleep is surely very curious : why 

 should flowers do so ; and why should some 

 flowers close at the approach of night, and 

 others not ? Moreover, flowers keep differ- 

 ent hours. The daisy opens at sunrise 

 and closes at sunset, whence its name 

 day's eye ; the dandelion opens at seven and 

 closes at live ; ear hawkweed is said to wake 

 at eight and go to sleep at two ; the scarlet 

 pimpernel wakes at seven and closes soon af- 

 ter two ; while Tropogon prafensis opens at 

 four in the morning and closes just before 

 twelve, whence its English name " John-go- 

 to-bed-at-noon." Other flowers, on the con- 

 trary, open in the evening. Now, it is ob- 

 vious that flowers which are fertilized by 

 night-flying insects w r ould derive no advan- 

 tage from being open by day ; nay, it would 

 be a distinct disadvantage, as rendering 

 them liable to be robbed of their honey and 

 pollen by insects not capable of fertilizing 

 them. Hence the lecturer believed that the 

 closing of flowers has reference to the hab- 

 its of insects. In support of this, he ob- 

 served that wind-fertilized flowers never 

 sleep, and that some of those flowers which 

 attract insects by smell emit their scent at 

 particular hours. 



Catching Cold. We find, in the Detroit 

 Review of Medicine, an account of Prof. 

 Rosenthal's researches on the effects of sud- 

 den changes of temperature, from which 

 we abstract a few very useful observations. 

 It has long been known that " colds " are 

 produced, not by lowness of temperature, 

 but rather by sudden changes from a higher 

 to a lower. The application of cold to the 

 surface of a healthy animal causes the cu- 



taneous vessels to contract, and then the 

 blood is prevented from circulating in the 

 skin, and confined to the interior of the 

 body, where it does not readily lose its 

 heat, but serves to supply warmth to the 

 vital organs. But, if the animal be exposed 

 to heat, the cutaneous vessels become di- 

 lated, and so remain after exposure to cold. 

 The blood is thus exposed in large amount 

 over a wide surface, and becomes rapidly 

 cooled, even though the temperature of 

 the surrounding medium is not very low. 

 A sudden passing from a heated room into 

 the cold outer air rapidly cools the blood 

 below the normal degree. As it returns 

 to the internal organs, it cools them much 

 more quickly than it would have done were 

 not the vessels dilated by previous warmth. 

 Thus a sudden cooling of the blood pro- 

 duces an irritating effect, or induces inflam- 

 mation in a way that a gradual alteration 

 would not do. To produce evil results the 

 cooling must be from above to below the 

 normal temperature. The effect of a chill 

 in causing inflammation may be due partly 

 to the effect of cold on the tissues them- 

 selves, and partly to the congestion (hy- 

 perasmia) which will occur in some parts 

 when the fluid is driven out of others by 

 the contraction of vessels. Rosenthal lays 

 most stress on the former of these effects. 

 It is a well-known fact that frequent cold 

 bathing or sponging enables one to bear 

 with impunity sudden changes of weather. 

 This is explained by the improved tone of 

 the vessels, produced by the cold applica- 

 tions. Thus, when exposed to heat, they are 

 not so relaxed that they cannot sufficiently 

 contract when necessary. 



Blow Plants are distributed. Some low 

 ground on the banks of the Delaware, below 

 the city of Philadelphia, having had a quan- 

 tity of mud from the channel of the river 

 spread over it, two species of plants, Poly- 

 gonum Orientate (an East Indian species), 

 and Cleome pungens (a West Indian species), 

 soon made their appearance in great num- 

 bers. During a discussion, in the Philadel- 

 phia Academy of Sciences, as to the prob- 

 able origin of the seeds of these plants, Dr. 

 Leidy expressed the opinion that as the 

 ground had long been used as a place of 

 deposit of ships' ballast, the seeds might 



