294 MORPHOLOGY. 



buds (A, c, b). Soon after vegetation has commenced in spring the bud 

 of the second leaf begins to develop, the portion immediately above its 

 point of attachment first expanding and pushing its way downward (fig. 

 1 78. B) ; in Morio in a roundish, in latifolia in a very early recognisable, 

 two-lobed form. This expansion soon breaks its way through the base of 

 the leaf, in the axil of which the bud occurs, as well as through the va- 

 ginal border of the lowest leaf, and thus it becomes visible externally. 

 The part by which the bud is connected with the stalk does not increase 

 in thickness, but merely elongates, whereby the pseudo-tuber, bearing the 

 bud above upon its summit, becomes continually removed further from 

 the parent plant. Toward the close of summer, the pseudo-tuber which 

 has vegetated in the preceding year has become wholly destroyed ; that 

 of the current year adheres to the side of the one newly produced, and 

 still bears the remains of its stalk and leaves : the new pseudo-tuber is 

 at least so far perfected that in the following year it is capable of forming 

 roots for the nutrition of the plant. In consequence of this kind of de- 

 velopment of buds, every Orchis plant alters its place annually ; and, since 

 the lower leaves have an angle of divergence of about 129, this occurs 

 in such a way, that in the fourth year it returns pretty nearly to its 

 original situation. These pseudo-tubers are decidedly not roots in a 

 morphological sense, in all probability not in a physiological ; but at present 

 we have no facts on which to found a decision on this question. On the 

 other hand, in the beginning of spring, many adventitious roots, which 

 subsequently take upon themselves the nutrition of the plant, are always 

 formed from the stem above the pseudo-tuber, and below the first leaf. I 

 have no accurate researches yet on the mode of cell-formation in all this 

 process. The pseudo-tubers are traversed by vascular bundles, which run 

 in great numbers, mostly in arcs, from the apex to the base, and are sur- 

 rounded by lax, large meshed, cellular tissue, which in an early condition ex- 

 hibits upon its walls reticular currents of sap proceeding from a cytoblast ; 

 cells from six to eight times larger lie embedded in the above, forming 

 circles round the vascular bundles. In very young pseudo-tubers the 

 homogeneous, colourless, and gelatinous contents of these larger cells is 

 tinged of a violet blue by iodine ; as the pseudo-bulb grows older, this 

 colour passes through the colour of red wine to yellow, and at last the 

 gelatinous matter exhibits no reaction to iodine. But during the vege- 

 tation of the same in the following year, the gelatinous matter changes 

 again in the reverse way, till at last, in the decaying pseudo-tuber, a con- 

 dition once more appears when the gelatinous substance is not coloured 

 by iodine. The surface of the gelatinous mass manifests in its perfect 

 stage of development markings of minute retriculations, almost granular, 

 somewhat like the starch in the cells of a boiled potato. In the remainder 

 of the cells a very finely grained starch is gradually formed, which dis- 

 appears almost totally during the vegetation of the pseudo-tuber, so that 

 at last only isolated granules remain in each cell, adhering to the persistent 

 cytoblast. This peculiar structure in our Orchidacece is to be paralleled 

 with some tubers in the tropical kinds, in which, in like manner, the form- 

 ation of a tuber only changes one single internode; for instance, Bolbophyl- 

 lum (fig. 179. A), Gongora, Rodriguezia, Epidendrum (fig. 179. B). 

 But in the tropical Orchidacece this structure passes through forms such 



next year's tuber ; d, lowest leaf of the plant ; e, second leaf, in the axil of which the 

 plant and tuber of the next year are formed ; f, adventitious roots cut off. B, Longi- 

 tudinal section through c of the preceding figure : , lower part of the leaf; b, rudi- 

 ment of the tuber which is formed out of the base of the axillary bud ; c, axillary bud, 

 the rudiment of the next year's plant. 



