58 Prof. Meyen*s Report of the Progress of 



the cork does not consist liere, as in the dicotyledons, of a di- 

 stinct hiyer, but rather of the layers of rind which have died 

 off. 



Many excellent memoirs have again appeared upon the 

 structure and design of the peculiar formations of rind, which 

 are now known under the name of lenticular glands. Mohl* 

 has enlarged his former observations on this subject, and has 

 especially noticed the relation of the lenticular glands to the 

 diJFereiit layers of rind. The lenticular glands are evident on 

 branches of even one year's growth beneath the uninjured epi- 

 dermis ; at a later period, sometimes towards the end of the 

 first year, at other times after some years, the epidermis over 

 the lenticular glands splits open in a longitudinal direction, 

 and the lenticular glands then make their appearance as little 

 warts. Subsequently they extend, artd they then appear as 

 diagonal stripes; where however the rind is thrown off, the 

 lenticular glands also fall off. The lenticular gland, says 

 Mohl, lies between the epidermis and the green parenchyma 

 of the rind, and consists of greenish or colourless cells, (some- 

 times it has a different colour, as for instance, a yellow in Ber^ 

 beris, and a red one in Sambucus nigra) which lie in rows, 

 having a position perpendicular to the axis of the branch, are 

 for the most part smaller than the cells of the green paren- 

 chyma of the rind, and unite towards the interior with it. In 

 many plants the cork layer of the rind, or its exterior paren- 

 chyma, is said to take a collateral part in the formation of the 

 lenticular glands, so that it consists, properly speaking, of 

 two layers, that is to say, of one belonging to the green paren- 

 chyma of the rind, and of one which consists of the exterior 

 parenchyma of the rind, or combines with it. Hence, as well 

 as from various other circumstances, Mohl places the forma- 

 tion of the lenticular glands parallel with the production of 

 cork ; nay, he supposes that the lenticular gland is a partial 

 cork formation, which owes its existence to the concretion of 

 the inner parenchyma of the rind. 



For my own part 1 cannot agree with these views. Obser- 

 vations on this subject have shown me that the lenticular gland 

 always consists in a concretion of the green layer of rind, and 

 that this concretion is only surrounded by the exterior paren- 

 chyma of the rind ; it is true, however, that there also takes 

 place a disjunction in the parenchyma, which forms the ex- 

 terior, and almost always reflexed margins of this enveloping 

 brown layer of rind. The cells of the lenticular glands, which 

 lie exactly in the middle, and which are distinguished from 

 all others by their length, generally lose by degrees their green 



• Observations on the Lenticular Glands. — Tubingen ,1836, 4to. 



