ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 813 



and vascular bundles, cell-division plays, in the first place, the most 

 important part, and afterwards the collenchymatous thickening ; more 

 rarely the two processes are simultaneous. The period when tho 

 thickening begins to manifest itself prominently depends on the 

 mechanical function which the collenchyma has to fulfil in the young 

 organs of the plant. 



It is not uncommon for the thickening of the cell-walls to be 

 accompanied by rounding off and disappearance of the intercellular 

 spaces. The septated collenchymatous fibres, which terminate at the 

 extremity of the stem in Lamium purpureum and Aesculus japonica 

 proceed from parenchymatous cells. Haberlandt found, on the con- 

 trary, that in Lamium purpureum, Atherurus ternatus, Cucurbita Pepo, 

 and Tradescantia erecta, the fibres originate from a generating pros- 

 enchymatous tissue formed by repeated longitudinal division of 

 merismatic mother-cells. In Chenopodium album the same observer 

 always found collenchyma originating from parenchyma. 



In none of the plants examined was the author able to detect a 

 closer genetic connection between the cells of the collenchyma them- 

 selves than between them and the adjacent parenchymatous cells. 

 Sanio, on the contrary, states, in the case of Euonymus latifolius 

 and Peperomia blanda, and Haberlandt in that of Tradescantia erecta, 

 that the collenchyma is derived from a single hypodermal layer of 

 cells. 



Stomata in a Fossil Plant.* — In a large series of fossil plants 

 obtained from the Turonian beds of the cretaceous formation from the 

 neighbourhood of Bagnois (Gard) R. Zeiller finds very well-pre- 

 served wood of a conifer closely allied to the Thuyites Hoheneggeri 

 Ettings. of the Wealden. In the ultimate branches or leaves, the 

 stomata may be exceedingly well made out ; and they are remarkable 

 for having, instead of a single fissure, an opening in the form of a 

 star with four or five rays. The stomata are formed of four, or less 

 often of five cells arranged in a rosette, the walls of which radiate 

 towards a central point, but leaving an orifice in the centre, in length 

 about one-third or two-fifths of the rays. The mechanism by which 

 the opening is produced is the same as in ordinary stomata, except 

 that four or five cells instead of two share in it. The stomatic 

 orifice occupies the bottom of a slight depression, though not so 

 well marked as in the allied recent Callitris quadrivalvis, Libocedrus 

 decurrens, and Frenela, and are usually surrounded, as in them, by a 

 slightly projecting margin of cuticle. The stomata are arranged 

 regularly in rows over the whole surface of the leaf. 



Spiral Cells in Crinum and Nepenthes.f — A. Trecul and L. 

 Mangin both describe, as the result of separate investigations, the 

 large spiral cells found by the first in several species of Crinum, by 

 the last also in Nepenthes phyllampJwra. In Crinum americanum they 

 are dispersed through all parts of the parenchymatous tissue of both 

 faces of the leaf, into the immediate neighbourhood of the large inter- 



* Bull. Soc. Bot. France, xxviii. (1S81) pp. 210-4. 

 t Ann. Sci. Nat. (Bot.) xiii. (1882) pp. 200-7 and 208-16 (1 pi.). 

 Ser. 2.— Vol. II- 3 i 



