330 SUMMARY OF CURRENT RESEARCHES RELATING TO 



into cells of about equal size containing as a rule an individual crystal." 

 In one specimen, Mallotus p/iiUppinensis, the raj-parenchyina contained 

 as many as four crystals in one cell. The micro-sections were immersed 

 in strong hydrofluoric acid without any effect upon the crystals, except 

 in the case of Strychnos arlorea, where they occur in great numbers in 

 special long pockets ; in this case the greater part of the crystals dis- 

 appeared. In Eucalyptus pilularis and Tristania conferta the " grit " 

 proved to be silica. The author finds no support for the theory that 

 crystals are characteristic of certain families or genera, since there is 

 great uniformity in those found in all Australian timbers, the only 

 variation being: in size and number. S. G. 



Structure and Development. 

 Vegetative. 



Fibro-vascular Formations in Monocotyledons. — A. Dauphine 

 {Ann. Sci. Natur. Paris, 1917, 20, 309-14, 1 pL). A study of the 

 development of the " supplementary " fibro-vascular 'formations in 

 Draaena indivisa and in D. Draco, in order to discover their relation- 

 ship to the secondary tissues of Dicotyledons. The author refers to the 

 marked similarity between the mode of secondary thickening in the 

 Chenopodiaceffi, and in such Monocotyledons as Dracdena. He compares 

 with the latter the formation of successive new generative layers in the 

 beet, showing that in this case the only real difference is that in Dracsena 

 the generative layer does not pass between the bundles. He also shows 

 that the greater part of the elements regarded as primary in Dicotyledons 

 really arise from secondary tissues. On the other hand, the alternate 

 primitive phase is found to be suppressed in Monocotyledons owing to 

 acceleration of development ; the normal generative layer has such a 

 brief duration of function that the elements beyond the primary bundles 

 are forced to assume the functions of the generative layer. Finally, he 

 finds a general unity of plan in the evolution of the conducting apparatus 

 of both Monocotyledons and Dicotyledons, which bridges over the 

 division formerly placed between the two groups. S. G. 



Growth of Trees.— A. Mallock {Froc. Roy. Soc, Ser. B., 1919, 90, 

 186-9!), 6 figs., 4 diagrams) has adapted the method employed for 

 observing the extension of cracks in buildings to finding the rate of 

 growth of timber-trees. This method depends upon the production of 

 bands of light, as a consequence of the illumination of sheets or prisms 

 of glass meeting at definite angles. By suitable means the shifting 

 of ^th of a band can be noted, and this corresponds to the extension 

 of iiyT) oiTofc^ of an inch of growth. The writer made observations day 

 and night on four trees between June 21 and the end of July, and found 

 that increase of girth was closely related to temperature ; growth was 

 most rapid when the temperature was at its lowest. Rain produces 

 great effect, even a shower resulting in an increase of girth. The eff'ect 

 of rain may be partly mechanical, being the result of the swelling of 

 the bark, but the checking of evaporation from the leaves appears to be 

 an important factor. In these experiments there was no means of 



