53 CELLULAR TISSUE. 



hirta, stricta, pinnata, verrucosa, &c.") are imbedded intramural glands; to the 

 structure of these attention had been drawn by Hildebrand ' in a description which 

 is not quite correct. 



If we compare the use of the word Gland by the different authors, and ask ourselves 

 what is really called a gland, we come to the conclusion that this name implies any part 

 of the plant from which something does or may come out, or in which something is 

 contained which, according to the conception of the author, is distinct from those 

 bodies which together form the generally distributed plant-substance which no plant is 

 without, as e.g. cellulose, starch, chlorophyll, &c. A consistent distinction does not 

 exist, since the pomt of excretion of the most heterogeneous bodies — air, water, calcium 

 salts, resin, sugar, &c.— of the most varying structure— epidermis, hairs, stomata, ends of 

 vascular bundles— and pointi of deposit, which are as variable in contents and structure, 

 viz. cells, groups of cells, intercellular spaces, are arbitrarily termed glands or not. 

 Compare e. g. Meyen, Secretionsorgane ; Treviranus, Physiologic, II. p. i, &c. ; Unger, 

 Anat. und Physiol, pp. 209-215 ; Martinet, Ann. Sci. Nat. 5 Sir. XIV. 



The facts which underlie this confusion of glands are, taken impartially, in the main 

 the following. At definite points, especially above the ends of vascular bundles, water- 

 pores, &c., water coming from below filters out on the surface, and bodies, such as sugar, 

 gum, salts of calcium, may occur in solution in it : the water gives the surface a moist 

 character, or evaporates and leaves the dissolved bodies behind as a solid excretion. 



Secondly, the surface may be moist, or sticky, or incrusted by bodies, which issue 

 directly from the epidermis itself, as e. g. the resin of the glandular hairs. 



Thirdly, both the above processes may combine on one and the same surface, as e. g. 

 on the glandular spots of the Acacias. 



The same bodies, which make the surface moist, or sticky, occur, in the fourth place, 

 also in the interior of the tissue, most variously distributed, sometimes in small quantities 

 in the protoplasm and cell-contents, sometimes filling whole cells, groups of cells, or 

 intercellular spaces. Thus, e. g. gum, resin. 



These four phenomena, that is the morphological facts which underlie them, are not 

 the only ones, but the most important of those upon which the use of the word gland is 

 based. It is true that those of the fourth category are distinguished as internal from the 

 others as external. On the physiological or teleological significance of these internal 

 glands hardly anything is known, and of the external ones but little. What is known 

 of the latter is sufficient for drawing a real distinction between definite categories. 

 A use of the collective name Gland in the sense used hitherto cannot therefore be 

 justified from the physiological or teleological point of view. Still less can this be 

 done on anatomical or morphological grounds, as is shown by what is said in this and 

 later paragraphs. If we wish, therefore, neither to retain the word gland in this sense 

 of an aver ready makeshift, nor to exclude it from vegetable anatomy, it only remains to 

 limit its use to definitely characterised anatomical phenomena, and further to distinguish 

 these in detail by special descriptions. As no one will support the first suggestion, while 

 the exclusion of the word is obviously impossible — vi'hat would become of pili glandu- 

 losi ? — we must adopt the third method. Since the parts of the epidermis, treated in this 

 section, on the one hand unquestionably constitute the great majority of the bodies 

 included in the term gland or glandular, and on the other hand correspond in very 

 definite anatomical characters with one another, while they differ from other parts, the 

 term gland, glandular should be applied to them, and in fact to parts of the epidermis 

 alone, whatever may lie below them. Whatever has not those anatomical properties, 

 should be called by a different name, which implies its position. Organs of similar 

 structure to those in question are very rare in places other than the epidermis : still 



• Compare De Candolle, Piodromus, II. p. 216. " Flora, i866, p. 81, Taf. II. 



