Digest of Current Literature. 79 



Type V. This is characterized by the formation of a secondary mass 

 of prosenchymatous tissue, hard, forming from one end to the other of 

 the rhizome, of Triglochin mariti?)iu?fi, for example, a soHd triangle of 

 pseudo liber-like tissue ; and similarly situated in other plants, as Schoe- 

 mis nigricans, Marsilea and Posidonia Caulini. 



Type VI. In this type the bundles in the branches, and also some- 

 times the rhizomes are provided with two tissues isolated and distinct. 

 One develops behind and near the air vessels, the other in front. A. 

 times there are many liber fibers as in certain Dioscorea. Example, 

 Tamus communis, L. 



In these two latter types there is usually an intermediate zone more 

 or less developed. 



The second part is a long exposition of the general anatomy of these 

 types of monocotyledons, of which not sufficient is given to furnish 

 material for a good resume. 



On the Application of the Microscope to the Study of Min- 

 eralogy. — Em. Bertrand. — This paper first describes how the apparatus 

 for measuring the angles of crystals, aleady noticed on page 76, can 

 be practically applied to the microscope, and also an improvement upon 

 its former construction. Then follow a few words about the study of 

 the optical properties of double refracting crystals by the microscope. 

 To determine the position of the axis of a crystal, four sectors of quartz 

 are mounted in the eye-piece with optical rotation alternately to the 

 right and left, and these, by their color, indicate the position of the 

 prisms. This has already been described in another journal. 



An arrangement is also described for using converging light with the 

 polariscope. 



A New Field of Study for the Microscopist. — Continued. 

 Ategiist 1878. 



Lymphatic Hearts. — Continued. 



Observations on the Termination of Motor Nerves, etc. — 

 Concluded. 



Preliminary Note on the Development of Blood and Ves- 

 sels. — Continued. 



The blood when it first appears is in vessels in no wise different in 

 structure from those of the adult ; the blood of the embr>'0 and of the 

 perfect animal has precisely the same properties. Authors consider 

 that the first rudiments of the heart or vessels cannot be distinguished 

 until they present endothelial elements, and that a collection of ele- 

 ments of indefinite character, having no other importance than that 

 they occupy the position of the heart, should not be regarded as a stage 

 in its development. 



In this paper the development of the heart is described until the 

 contraction begins and circulation is established. 



