182 THE AMEEICAN MONTHLY. [August, 



Moreover, and this is an original and novel observation of Mr. Dienelt, 

 in those larger tracheae of the water scorpion which are devoid of hairs 

 there are instead a series of rounded or irregularly oval spaces in the 

 spirals thus : =@=. Whether they occur in any other trachea is not yet 

 known. The Belostoma, a relative, shows neither these nor the hairs 

 in its trachese. 



The intra-tracheal hairs have been verified thus far in only some half- 

 dozen insects, while Dujardin's list is much larger. 



What purpose these intra-tracheal hairs can serve is not clear. Mr. 

 Dienelt oflers the explanation " that they are used in oxygenating the 

 blood acting through their walls similar to the action of the capillaries 

 in our lungs. The surface exposed to the air in the tracheje is im- 

 mensely increased by these tubes." 



Plausible though this may appear, the theory is open to weighty ob- 

 jections, but these I refrain from advancing now without further inves- 

 tigation and greater presumptive proof. 



Again, what appears to be quite a new discovery by Mr. Dienelt 

 and a curious fact is that in certain instances the spiral structure of the 

 tube may be interrupted, and the missing turns be replaced by a mem- 

 brane beset with hairs. This is shown upon a slide from a wood-bor- 

 ing lepidopterous larva which the observer kindly forwarded to me. 

 The band in this instance is of a breadth equal to six or seven of the 

 spirals, and the intra-tracheal hairs are strictly limited to this band. In 

 this instance, then, these bodies can have little or nothing to do with 

 aeration of the blood. The same characteristic is likewise shown upon 

 a slide of tracheae from the silk-worm in my cabinet. Other observa- 

 tions will be required to indicate the physiology of these hairy bands, 

 for thus far they appear devoid of muscular fibres. Ai"e they, perhaps, 

 like elastic tissue.'' 



Enough, it is hoped, has been^here recorded to show that the com- 

 monplace tracheae are still a field fit to yield new fruits to the studious 

 observer. 



o 



Collecting Specimens on the Desert of Atacama. — Our 



botanical friends will find delight in an article in the Februaiy 

 number of the Bulletin of the Torrey Botanical Club, from the pen of 

 Thomas Morong, written in his happiest style. It describes a collect- 

 ing trip to the Desert of Atacama. Particularly worthy of note are his 

 remarks upon the adaptation of plants to an almost rainless climate. 

 These desert plants develop an immense number of seeds. The seeds 

 have a very thick coat, which, nevertheless, softens readily under the 

 influence of moisture. Bulbs are so juicy that the juice can be squeezed 

 out in a stream by hand. Plants begin to bloom and fruit at a very 

 early age. Finally, the shrubs shed their leaves in the summer instead 

 of the winter, thereby reducing their vital expenditure to a minimum 

 at a season when they need to husband their utmost strength in order 

 to resist long continued dryness. 



Personal.— Dr. H. M. Whelpley, F. R. M. S., has been elected 

 Professor of Physiology and Histology and Director of the Histological 

 I^aboratory of the Missouri Medical College. The doctor is also Pro- 

 fessor of Microscopy in the St. Louis College of Pharmacy and Editor 

 of the Meyer Brothers' Druggist. 



