762 



THE POPULAR SCIENCE MONTHLY. 



mer of 1871, had confined the larvae of va- 

 rious species of moths, and neglected to 

 supply them with food for four or five days. 

 These larvae had advanced toward their final 

 change, possibly within a week or ten days. 

 When the box was opened, the greater num- 

 ber were found in cocoons, while the remain- 

 der wandered about, as if in quest of food. 

 The latter the author removed to another 

 box, where they were provided with abun- 

 dance of food. After three or four days 

 they began to assume the chrysalis form. 

 The first batch proved to be males without 

 exception, while the last batch proved, with 

 but two exceptions, to be females. (The 

 whole number in the two batches was about 

 sixty.) 



Mr. Gentry then details further experi- 

 ments made by him to decide this question, 

 and states that the result was always the 

 same. He adds the following facts, which 

 came under his notice in the course of his 

 observations and experiments : 1. That 

 males are the invariable result when the 

 larvae are fed on diseased or innutritious 

 food ; 2. That in the fall, when the leaves 

 have not their usual amount of sap, males 

 are generally produced ; 3. That more males 

 are produced late in the season than fe- 

 males ; 4. That the sexes, in early life, can- 

 not be distinguished, the change being 

 brought about, late in life, by the conditions 

 of nutrition. 



Intensity and Patience required in Sci- 

 entific Work. — Whether in original work or 

 in elaborating work already done, scientific 

 labor, when conscientiously performed, is 

 necessarily slow and exhausting. M. de 

 Candolle, the great French botanist, has re- 

 cently brought to a conclusion, with the sev- 

 enteenth volume, his great " Prodrome of 

 Plants," stopping at the completion simply 

 of the Dicotyledones. It was begun by his 

 illustrious father, Augustin Py ramus de 

 Candolle, about 1816, who worked at it 

 until his decease, in 1841. It was con- 

 tinued by his son Alphonse, who called to 

 his aid other famous botanists, his son Ca- 

 simir among them. With true naivete the 

 author pleads necessity of stopping at the 

 point now reached — " ne tertiam botanicorum 

 generationem occideret!" — lest the under- 

 taking should kill off a third generation of 



botanists. In a supplemental pamphlet he 

 gives his opinion that the Phanerogams, es- 

 timated at 110,000 species, might, by dis- 

 tributing the task among twenty-five botan- 

 ists, be worked up in about fifteen or six- 

 teen years. He says that in his father's 

 time one could elaborate at the rate of ten 

 species a day, but that now a faithful mon- 

 ographer (or specialist), under the modern 

 requirements, can seldom exceed 300 or 

 400 species per annum — that is, about one 

 species a day ! 



Rationale of Double Flowers. — That the 

 tendency in plants to produce double flow- 

 ers is a natural one, and not exclusively 

 evoked by the florist, is shown by Mr. 

 Thomas Meehan, in a communication to 

 the Philadelphia Academy of Natural Sci- 

 ences. Many of the commonest wild flow- 

 ers, which no one would think of cultivating, 

 have double flowers in cultivation, which 

 were no doubt originally found wild ; for 

 instance, various species of ranunculus. 

 The author had himself placed on record 

 the discovery, wild on the Wissahiekon, 

 of a double Saxifraga Virginica, and Dr. 

 James Darrach had found in the same loca- 

 tion a double-trailing arbutus. There are in 

 plants two methods by which double flow- 

 ers are produced. The axis of a flower is 

 simply a branch very much retarded in its 

 development, and generally there are, on 

 this arrested branch, many nodes between 

 the series forming the calyx, or corolla, 

 and the regular stamens and carpels, which 

 nodes are entirely suppressed. But, when 

 a double flower is produced, sometimes 

 these usually suppressed node3 become de- 

 veloped, in which case there is a great in- 

 crease in the number of petals, without any 

 disturbance in the staminal characters. But, 

 at other times, there is no disturbance of 

 the normal character of the axis. This was 

 the case with the trailing arbutus discov- 

 ered by Dr. Darrach. 



Land-Plants in Lower Silurian. — It has 



hitherto been supposed that the Silurian 

 age was one in which an absolutely un- 

 broken ocean enveloped the earth. Dr. 

 Dawson made it probable that land-plants 

 existed in the Upper Silurian, or latter Silu- 

 rian age. Leo Lesquereux, in American 



