90 THE AMERICAN MONTHLY [April, 



Diseases of Swine. — The Commissioner of Agriculture has ap- 

 pointed a commission, consisting of Professor William H. Welch, of 

 Johns Hopkins University, Dr. E. O. Shakespere, of Philadelphia, 

 and Professor T. J. Burrill, of the University of Illinois, to investigate 

 the subject of swine diseases in the United States, and the methods 

 of their treatment and prevention. 



"Water Supplies Again. — The North American Review for Feb- 

 ruary, in its " notes and comments," gives some crisp points upon 

 this subject, some of which are, to say the least, overstated, but many 

 of which deserve consideration. 



A New Moss. — Prof. C. R. Barnes publishes in the Bot. Gaz. (vol. 

 xiv, p. 44) a list of mosses from the Mingan Islands on the southern 

 shore of Labrador, among which is a new species which he names 

 Bryum Knoivltoni . 



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Certain Relations of the Cell-wall. — Dr. Kohl {Bot. Central,\o\. 

 xxxvii, p. 1) demonstrates that the growth in thickness of the hairs of 

 many plants is not strictly by intersception nor by opposition, but by 

 periodic deposition of layers of cellulose, and he notes the fact that, be- 

 tween these successive layers, there is generally a trace of protoplasmic 

 matter not easily detected by Millon's reagent. Kravon has already 

 shown that the growth of vast fibres is substantially of the same char- 

 acter. 



Lichens and Their Hosts. — No subject perhaps affords the ama- 

 teur worker with the microscope abetter illustration of what the instru- 

 ment has aided the scientist in doing than does the progress which has 

 been made in the study of the lichens and the microscopic algae upon 

 which some species of lichens feed. The Am. Nat. for May presents 

 an interesting sketch of progress of investigation in this direction from 

 the pen of Thos. A. Williams. The green bodies which are found in 

 great abundance in the tissues of many lichens w T ere supposed to be a 

 part of the lichen and were named gonidia. Long continued observa- 

 tion and experiment showed, however, that this was not the case, and 

 after many patient and oft repeated cultures of the so-called gonidia it 

 has been found that they have a life history entirely independent of the 

 lichen, and are therefore to be classed among other plants. It is found 

 moreover that these so-called gonidia represent certain groups of chloro- 

 phyll bearing plants among the Protophyta and Zygophyta, and many 

 are easily identified with well-known species of these algae or chloro- 

 phylt bearing plants. The nature of the relation of the gonidia to the 

 lichen is shown by the culture of the spores of those lichens in which 

 the gonidia are found. If the spores of these lichens are subjected to 

 the proper conditions of warmth and moisture they will germinate in 

 the course of a few days and growth will continue for a time, after 

 which it will cease unless the germinating hyphea of the lichen comes 

 in contact with algae upon which it can feed, in which case the growth 

 continues. 



