Most of the cells, however, included hyaline, motionless little spheres, which did not seem to consist of protoplasm, but, I suppose, of some balsam or essential oil.
Pelargonium zonale (var. edged with white).--The leaves [page 351] are clothed with numerous multicellular hairs; some simply pointed; others bearing glandular heads, and differing much in length. The glands on a piece of leaf were examined and found to contain only limpid fluid; most of the water was removed from beneath the covering glass, and a minute drop of one part of carbonate of ammonia to 146 of water was added; so that an extremely small dose was given. After an interval of only 3 m. there were signs of aggregation within the glands of the shorter hairs; and after 5 m. many small globules of a pale brown tint appeared in all of them; similar globules, but larger, being found in the large glands of the longer hairs. After the specimen had been left for 1 hr. in the solution, many of the smaller globules had changed their positions; and two or three vacuoles or small spheres (for I know not which they were) of a rather darker tint appeared within some of the larger globules. Little globules could now be seen in some of the uppermost cells of the pedicels, and the protoplasmic lining was slightly separated from the walls of the lower cells. After 2 hrs. 30 m. from the time of first immersion, the large globules within the glands of the longer hairs were converted into masses of darker brown granular matter. Hence from what we have seen with Primula sinensis, there can be little doubt that these masses originally consisted of living protoplasm.
A drop of a weak infusion of raw meat was placed on a leaf, and after 2 hrs. 30 m. many spheres could be seen within the glands. These spheres, when looked at again after 30 m., had slightly changed their positions and forms, and one had separated into two; but the changes were not quite like those which the protoplasm of Drosera undergoes. These hairs, moreover, had not been examined before immersion, and there were similar spheres in some glands which had not been touched by the infusion.
Erica tetralix.--A few long glandular hairs project from the margins of the upper surfaces of the leaves. The pedicels are formed of several rows of cells, and support rather large globular heads, secreting viscid matter, by which minute insects are occasionally, though rarely, caught. Some leaves were left for 23 hrs. in a weak infusion of raw meat and in water, and the hairs were then compared, but they differed very little or not at all. In both cases the contents of the cells seemed rather more granular than they were before; but the granules did not exhibit any movement. Other leaves were left for 23 hrs. in a solution of one part of carbonate of ammonia to 218 of water, and here again the granular matter appeared to have increased [page 352] in amount; but one such mass retained exactly the same form as before after an interval of 5 hrs., so that it could hardly have consisted of living protoplasm. These glands seem to have very little or no power of absorption, certainly much less than those of the foregoing plants.
Mirabilis longiflora.--The stems and both surfaces of the leaves bear viscid hairs. young plants, from 12 to 18 inches in height in my greenhouse, caught so many minute Diptera, Coleoptera, and larvae, that they were quite dusted with them. The hairs are short, of unequal lengths, formed of a single row of cells, surmounted by an enlarged cell which secretes viscid matter. These terminal cells or glands contain granules and often globules of granular matter. Within a gland which had caught a small insect, one such mass was observed to undergo incessant changes of form, with the occasional appearance of vacuoles. But I do not believe that this protoplasm had been generated by matter absorbed from the dead insect; for, on comparing several glands which had and had not caught insects, not a shade of difference could be perceived between them, and they all contained fine granular matter.