198 THE ZOOLOGIST. 



to the first of these papers were originally made many years ago on 

 Euphorbia pephis, and have now been extended to other genera. A plant 

 of E. pephis having been dug up and carefully washed, the smaller rootlets 

 may be placed under the microscope without further preparation, the thicker 

 roots may be examined by means of sections. If such roots are left, before 

 being examined, in a solution of carbonate of ammonia (1 to 7 per 1000) for a 

 short time (varying from a few minutes to several hours), they present a wonder- 

 fully changed appearance. The most striking alteration is that the surface 

 of the root assumes a longitudinally striped appearance, due to longitudinal 

 rows of darker brown cells, alternating with lighter-coloured rows. The 

 darker colour is seen under a higb power to be due to the presence of 

 innumerable rounded granules of a brown tint, which the lighter-coloured 

 cells are without. Similar brown granules are deposited in cells scattered 

 throughout the parenchyma, and markedly in the elongated endoderm cells 

 surrounding the vascular bundle. The granules are apparently neither 

 resinous nor fatty, for they are not removed by alcohol or ether; they 

 are, however, slowly acted on by caustic potash, and seem to be of the 

 nature of protein. The most remarkable part of the phenomenon is 

 that the granules are only formed in some of the external cells, and 

 that these cells are, before the treatment with ammonia, indistinguishable 

 by their shape or by their contents from their fellows, which are un- 

 affected by the solution. There is, however, a curious functional difference 

 between the two classes of cells, namely, that the granular cells do not 

 produce root-hairs, which arise exclusively from the cells of the light- 

 coloured rows. Effects similar to those now described were observed in 

 some other Euphorbiaceous plants, e.g.. PhyUemthtu compressor, though 

 not in all the genera of this family which were observed. Among genera 

 belonging to other families may be mentioned Drosopkyllwn and Cyclamen, 

 as showing the phenomenon especially well. Altogether 49 genera were 

 observed; of these 15 were conspicuously acted on, and 11 in a slight 

 degree, making together 26 genera, while the roots of the remaining 23 

 genera were not acted on in any plain manner. 



The view suggested by Mr. Darwin is that the granular matter is of the 

 nature of an excretion, the arrangement of the dark-coloured cells in rows 

 agreeing with what is known of the disposition of certain cells whose 

 function admittedly is to contain excretions. The granules, moreover, are 

 deposited in the loose exfoliating cells of the root-cap, where they cannot 

 take part in the life of the root; and this fact points in the same direction. 



In his second paper, above referred to, Mr. Darwin adduces facts to 

 prove that carbonate of ammonia causes a kind of aggregation in chlorophyll 

 bodies, and as these are protoplasmic, the belief in the protoplasmic nature 

 of the aggregateed masses in Drosera and other carnivorous plants is 

 supported. 



