PROGRESS OF MICROSCOPICAL SCIENCE. 237 



of the primordial follicles from tubes. He describes a somewhat 

 complicated histological process in which the follicles undergo a 

 physiological destruction ; this commences with a fatty degeneration 

 of the follicular walls, and proceeds with contraction of the cavity till 

 it is completely obliterated. The young tissue by which this ob- 

 literation is eifected is considered by M. Slayjansky to proceed from 

 the white corpuscles of the blood. In regard to the formation of the 

 corpus luteum (verum and spurium) he concludes that in this process 

 only the so-called granulation layer of the follicular wall is active, the 

 membrana gi-anulosa undergoing fatty degeneration and atrojihy. In 

 conclusion, he describes the pathological conditions of the ovary, with 

 the exception of dropsy of the Graafian follicles. He divides them 

 into affections of the parenchyma, and affections of the wall of the 

 follicle. The former are included under the heads of fatty meta- 

 morphosis and colloid metamorphosis ; the latter he considers may be 

 embraced imder the general head of sclerosis. 



Tlie Structure of Stigmaria has been most fully gone into in a paper 

 by Professor "Williamson, F.E.S. (of St. John's College) in the last 

 number of the ' Proceedings of the Eoyal Society.' Stigmaria is shown 

 to have been much misunderstood, so far as the details of its structure 

 are concerned, especially of late years. In his memoir of Sigillaria 

 elegans, published in 1839, M. Erongniart gave a description of it, 

 wluch, though limited to a small portion of its structiu'e, was, as far as 

 it went, a remarkably correct one. The plant now well kno^ATi to be 

 a root of SigiUaria, possessed a cellular pith without any trace of a 

 distinct outer zone of medullary vessels, such as is universal amongst 

 the Lepidodendra. The pith is immediately siu-rounded by a thick 

 and well-developed ligneous cylinder, which contains two distinct sets 

 of primary and secondary medullary rays. The primary ones are of 

 large size, and are arranged in regiilar quincunctial order ; they are 

 composed of thick masses of miu'al cellular tissue. A tangential 

 section of each ray exhibits a lenticular outline, the long axis of 

 which corresponds with that of the stem. These rays pass directly 

 outwards from pith to bark, and separate the larger woody wedges 

 which constitute so distinct a feature in all transverse sections of this 

 zone, and each of which consists of aggi-egatod laminae of barred 

 vessels disposed in very regular radiating series. The smaller rays 

 consist of vertical piles of cells, arranged in single rows, and often 

 consisting of but one, two, or thi-ee ceUs in each vertical series ; these 

 latter are very niimerous, and intervene between all the numerous 

 radiating laminte of vessels that constitute the larger wedges of woody 

 tissue. The vessels going to the rootlets are not given off from the 

 pith, as Goeppert supposed, but from the sides of the woody wedges 

 bounding the upper part of the several large lenticular medullary 

 rays, those of the lower portion of the ray taking no part in the con- 

 stitution of the vascular bundles. The vessels of the region in question 

 descend vertically and parallel to each other untU they come in contact 

 with the medullary ray, when they are siuldeuly deflected, in large 

 numbers, in an outward direction, and nearly at right angles to their 

 previous course, to reach the rootlets. But only a small number reach 

 their destination, the great majority of the deflected vessels terminating 



