298 PHYSIOLOGICAL BOTANY. 



he considers to be an exostome is rather a stigma. A 

 detailed Criticism of this paper, by Dr. Gottsche, of 

 Altona, is given in the Bot. Zeitung., 1845, pp. 366, 

 377, 398, 413, 433, 447, and 507, which contains much 

 remarkable matter, and therefore deserves great attention. 

 Thus it contains a minute examination of the ovule of 

 Encephalartos lonyi/olius, with comparative observations 

 upon other Cycadea3 and Coniferse. We cannot follow 

 the author in his investigations, for this would require a 

 separate memoir. 



Upon the Structure of a full-grown Stem of Cycas cir- 

 cinalis. By F. A. W. MIQUEL. Linnaea, 1844, p. 125, 

 tab. 4, v, 6. A good description of a full-grown living 

 stem, of which we were not before in possession. The 

 internal structure is especially remarkable ; it consists of 

 a cortical parenchyma, which is composed of three layers 

 of cells. The wood is divided into concentric, unequal 

 and irregular layers, which are separated from each other 

 by thicker or thinner layers of parenchymatous cells, con- 

 taining starch. Each woody layer is divided into almost 

 quadrangular or club-shaped woody portions by distinct 

 medullary rays. On examining the large woody layers, 

 we find that they take a very serpentine course. Those 

 vessels which assume a lateral direction, perforate the 

 bark, and run to the scales and leaves. All the vessels 

 of the wood are dotted. Some of the roots were cut off, 

 but they entirely agreed in structure with the stem. In 

 my ' Icon. Sel. Anat. Bot./ vol. ii, I have already shown 

 the difference between the structure of Dicotyledons and 

 the Cycadese ; the vessels do not ascend directly upwards, 

 as in the Dicotyledons, and they traverse all parts of the 

 bark towards the leaves and scales, which is only the case 

 in Dicotyledons at individual buds. More recently I 

 have endeavoured to show, in a short memoir read before 

 the Academy of Sciences, that the scales are in fact 

 leaves, and that the so-called leaves are branches. This 

 renders the germination, especially, very intelligible. 



