816 REPORT—1904. 
chemistry the work of penetration and localisation which the microscope performs 
for structure. 
For a long time botanical microchemistry has dealt with a limited number of 
bodies and reactions: cellulose, starch, reducing sugars, inulin, proteid matters, 
asparagin, tannins, silica, and calcium compounds. Gradually a series of interest- 
ing bodies have been added to the original scanty list, such as sulphur, glycogen, 
salts of iron and other bases, alkaloids, myrosine, certain glycosids, prussic 
acid, &c. 
Although a few valuable preliminary researches had already appeared, a more 
methodical attempt to localise, in the various tissues, the important group of 
alkaloids was made in a paper I published in 1887 in collaboration with two of 
my pupils, Dr. Maistriau and the lamented Dr. Clautriau. We used a great 
number of general as well as special reagents of the different alkaloids which we 
examined, for the sake of their mutual control. In consequence of the fact that 
many alkaloids are closely related to proteids, a great analogy exists in the action 
of many general reagents on both classes of compounds. This is, of course, a 
serious difficulty in microchemical determinations. But an alcoholic solution of 
tartaric acid separates clearly the two groups, dissolving the former from the cells 
and leaving the latter undissolved, and this method has always given very good 
results. 
Similar lines of investigation have been followed with success within the last 
eighteen years by a number of my pupils and by many other observers, principally 
in Holland and Sweden, but also in France, Germany, and Italy. 
The more important conclusions arrived at by these researches (which must, 
of course, be conducted critically) might be summarised as follows :— 
(1) The qualitative and to some extent the quantitative distribution of alka- 
loids (especially those belonging to the pyridic series) can be determined micro- 
chemically in the various organs of plants with perfect certainty. 
(2) In living cells the alkaloids are eliminated from the protoplasm and 
gather in the vacuole. It is only in cells which have lost all their liquid contents 
(as in ripe seeds) or in dead cells that they accumulate in the protoplasm or the 
cell-wall. 
(8) The alkaloids are generally localised : 
(a) In very active tissues: chiefly in the neighbourhood of growing points 
(a little behind the initial cells), in the ovules, &c. ; 
(6) In the epidermis, the epidermic hairs, often also in the sub-epidermic 
layers of vegetative organs, as well as the outer layers of fruits and seeds; 
(ce) Round the fibro-vascular bundles, in certain of their phloem-elements and 
in the neighbourhood of the pericycle ; 
(d) In the phellogen and the youngest cork-cells (either normal or consecutive 
to traumatism) ; 
(e) In the laticiferous or similar elements, when present. 
(4) By means of the microchemical tests many new alkaloid-plants have been 
discovered, the result being afterwards confirmed by the usual chemical methods, 
e.g. certain Orchidacese (where alkaloids were formerly quite unknown), Amaryl- 
lidaceze, Papaveracese, Ranunculacee, Solanacez, &c. 
(5) Although the investigation of animal tissues is particularly delicate, obser- 
vations (yet unpublished) show that even here a microchemical identification of 
organic bases is sometimes possible—for instance, in Salamandra, 
(6) Granting that the physiology of alkaloids is far from settled, I think a 
critical study of their topography as well as their behaviour in germination, 
growth, etiolation, maturation of seeds, &c., supports the view that they are 
waste-products, resulting from the catabolism of cytoplasm, and secondarily 
utilised for defence against animals. A few grams of an alkaloid constitute a 
protection not less efficient than the strongest spines. 
The diminution of the proportion of alkaloids in a given plant is often wrongly 
interpreted as a proof of their direct consumption as plastic material, But the 
