140 PROGRESS OF MICROSCOPICAL SCIENCE. 



believes that in every known instance the gonidia of lichens can be 

 produced upon a species of Alga. See also ' The Academy ' (July). 



Tlie Epidermis of the Tway-Uade. — Mr. Gulliver, F.E.S., who is so 

 well known for his researches into the structure of plants, lately gave 

 a lecture to one of the provincial societies on the above subject. He 

 stated, says ' Science Gossii) ' (July), that though the epidermal cells of 

 plants often afford good diagnostic characters, it is remarkable that 

 they have been little used. The object of the present communication 

 was to show that these cells of Listera ovata differ from those of other 

 orchids. In this species, the epidermal cells on the under surface of the 

 leaf have remarkably sinuous boundaries, so as to form a good example 

 of that common kind of epidermis which botanists have named Colpen- 

 chyma, while on the upper surface of the leaf of that same plant the 

 cells have smooth margins, more or less polygonal from mutual pres- 

 sure of roundish or oblong cells. Thus, besides the stomata on the 

 under side of the leaf, the epidermis of the two sides differs so plainly 

 and curiously as to present very pretty microscopic objects. At the 

 same time, for comparison, examinations were made of the correspond- 

 ing tissue of Orchis mascula, Orchis fusca, Ophrys muscifera, and Ophrys 

 aranifera, in every one of which the epidermal cells, on both the upper 

 and under sides of the leaf, were much alike and — save the stomata 

 on the under surface — resembling the same cells on the upper side of 

 the leaf of the T way-blade. To define the exact value of this charac- 

 ter would require an examination of the wilderness of exotic orchids 

 as v>'ell as all our native species ; but the remarkable character now 

 described suggests a wide and probably fertile field for future cultiva- 

 tion. At jDresent we know that, among the Duckweeds, Lemna minor 

 is easily distinguishable, by its sinuous epidermal cells, from Wolffia 

 arrhiza, though these two plants were formerly considered as identical. 



The Embryo Phfs-head. — Mr. W. K. Parker, F.E.S., has given a 

 very valuable paper on this subject to the Eoyal Society. It will, 

 we suppose, be published in the ' Transactions.' Meanwhile, we take 

 the following account from the last number of the ' Proceedings of the 

 Royal Society.' The number of embryo skulls examined is something 

 surprising. 



The most important results of the j)resent investigation may be 

 stated as follows : — 



1. In a pig-embryo, in which the length of the body did not exceed 

 two-thirds of an inch, and four postoral clefts were present, the 

 craniofacial skeleton was found to consist of : — (a) The notocbord, ter- 

 minating by a rounded end immediately behind the pituitary body. 



(h) On each side of the notochord, but below it, there is a cartila- 

 ginous plate, wliich in front ends by a rounded extremity on a level 

 with the apex of the notochord, while behind it widens out and ends 

 at the free lower margin of the occiijital foramen. These two plates, 

 taken together, constitute the " investing mass " of Rathke. In this 

 stage they send up no i)rolongations around the occipital foramen ; in 

 other words, the rudiment of the basioccipital exists, but not of the 

 ex(x;cipital or supcroccipital. 



