Vegetable Physiology for the Year 1836. 59 



colouring, and at last become quite white, as the green con- 

 tents gradually disappear. These middle cells stand with 

 their extended longitudinal axis quite horizontal ; whereas the 

 cells of the lenticular gland, which form its exterior layers, 

 generally retain not only their usual form, but also more or 

 less their green colouring. If the entire formation gradually 

 dries, its cellular membranes become more or less coloured ; 

 and in this colouring only has the tissue of the lenticular glands 

 any resemblance to the formation of cork. 



Mohl once more notices in this memoir the opinion which 

 De Candolle has diffused so generally, that the lenticular 

 glands were to be considered as it were root-buds, an opinion 

 which we find in almost all the recent popular writings on 

 vegetable physiology, although this position ought long since 

 to have been abandoned. Unger also, in his very interesting 

 dissertation on the design of lenticular glands*, states that these 

 organs only occasionally stand in connection with the cortex ; 

 but they are not in any respect, according to Unger, " espe- 

 cially theexterior flat-pressed cells of the cortex only, i. e., those 

 which are united by a gelatinous mass (materia inter cellular is) 

 to a kind of integument (z. e, the external layers of the cortex) 

 those which take any part in this metamorphosis," but the whole 

 formation proceeds from the green layer of cortex, and breaks 

 right through the external integument, just as Unger has cor- 

 rectly figured it in the above-mentioned memoir. Unger thinks 

 that the first momentum of the formation of the lenticular 

 glands is a concretion of the wide-pressed cells of the exterior 

 layer of cortex. The concretion begins with the increase in 

 size of the single cells ; the increase in size causes a loosening 

 of the concretion, and its final consequence is a complete 

 separation. A nominal increase of cells is said to take place 

 from the intercellular matter (!), and in this may principally 

 be the proximate cause of the bursting of the upper layers of 

 cells. Unger has very well observed that the cells which form 

 the interior of the lenticular gland separate from one another, 

 and seem as it were to make themselves independent. (Where 

 then in this case has the intercellular matter remained, which 

 is said to inclose these cells?) When the concrete masses 

 are very great, and do not pulverize, they form great warts, 

 such as we can point out on JLuonymus verrucosus and others. 



Unger enumerates various other vegetable formations, where 

 he recognised an analogue to the formation of lenticular glands, 

 in order perhaps in this way to be able to unravel their real 

 design. In the first place are mentioned as such analogous 

 formations, those remarkable organs which Von Martius dis- 

 * Flora of 183G, pp. 577 to 604. 

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