230 REPORTS ON inve;stigations and trojects. 



other trunks the true condition may be exactly determined, whether indicat- 

 ing simply the bisporangiate or else dioecious fruits of two seasons of fructifi- 

 cation or, as the remaining alternative, a more or less distinct monoecious 

 monocarpy. In any case it is once more brought forcefully home to us that 

 the study of the young fruits yields much of interest, and that in dealing with 

 fossil cycads every phase of angiospermous sporophyll arrangement may 

 sooner or later be found repeated. 



In these later studies the seeds have been receiving the special study 

 merited by their morphologic interest and value as pointed out in the prefa- 

 tory note to the volume in structure — the avowed effort, despite the labor 

 involved, being to exhaust the possibilities afforded by the collections for 

 such study, either direct or comparative. It is of primary interest to note 

 that here, for the first time in the case of any fossil plant, the cotyledonary 

 bundle pattern has been determined. Intermediate in form to that of the 

 existing cycads and Ginkgo, it exhibits a degree of reduction not equaling 

 that of the conifers, but showing a remarkable similarity to the more primi- 

 tive of the angiosperms in the lateral strand elimination and entire form ; 

 whence we derive yet another of the cumulative proofs that Cycadeoidean 

 fructification indicates in all larger outlines the true manner of angiospenn 

 evolution. Taken in entirety, the series of sections demonstrating these facts 

 of fundamental interest must without any qualification be the most complete 

 ever worked out and brought together to illustrate genera, species differentia- 

 tion, and fructification in a group of extinct plants. 



Early persuaded of the interest of the cycadophytes from every scientific 

 point of view, persistent effort has been made to carry their study beyond 

 the boundaries of countries and the far severer limits of existing collections. 

 The task is to link together the really little-understood silicified trunks, Wil- 

 liamsonia fruits, and ubiquitous cycad foliage of the Mesozoic, as far as may 

 be, into a connected whole which can yield its full quota of stratigraphic and 

 structural interest and fact. 



PHYSICS. 



^ Barus, Carl, Brown University, Providence, Rhode Island. Grant No. 630. 

 Continuation of study of the properties of condensation nuclei, including 

 ions. (For previous reports see Year Books Nos. 4, 5, 7, and 8.) $500 



In connection with his work on the coronas as a means for the study of 

 nucleation, Professor Barus came across a principle of interferometry which 

 seemed of sufficient importance to justify special investigation. This has 

 been done and what appears to be a very promising new procedure in inter- 

 ferometry has been developed. The report is nearly ready for publication. 



The method consists in bringing to interference two complete diffraction 

 spectra (components) from the same source of light. This may be done in a 

 variety of ways, either directly or by using the devices of Jamin, Michelson, 

 and others for separating the components. 



