Mr. J. .Micrs on the External Coatings of Seeds. 357 



continuous with the coat in question, the raphe being a ma-e 

 thickening of that coat, in all the cases which liave come under 

 our observation. We have never seen such conditions as arc 

 represented in fig. 1 of Mr. Miers's paper, where the testa is 

 shown distinctly separated from the raphe (or ])laccntal sheath). 

 The cellular structure is uninterruj)tcd between raphe and testa 

 where the two are in contact, and the hue of division running 

 down between b and c has no cvistcnce in any case that we have 

 observed. 



7. Consequently there is no necessity that branches of the 

 ruphal vessels must set out from the gangylode or chalaza to 

 enter the testa ; they may be sent out laterally in any part of 

 the raphe between the hilum and the chalaza. 



8, 9 and 10 fall away, if the foregoing statement be correct. 

 We do not venture to assert tiiat it is universally true, but it is 

 the correct account of what we have found to exist in a large 

 number of cases. 



As regards specialities referred to in the paper, we must de- 

 clare in favour of the superior value of such evidence as that 

 furnished by Dr. Gray, in the case of Magnolia, to any analogical 

 reasoning, which, in the case of the changes occurring during 

 the maturation of seeds and fruits, is a most unsafe guide. And 

 when Mr. Miers finds a difficulty in comprehending how an 

 originally homogeneous tunic becomes developed into a double 

 layer, one hard and the other soft, we think he must have over- 

 looked the familiar case of the fruits of the Amygdalea, where 

 the stone and pulp are clearly produced from the simple pericarp. 



The cases where a branching of the vascular structure from 

 the hilar end of the ovule takes place, are most simply explained 

 on the above grounds, as developments within the substance of 

 the testa ; and the " placentary sheath" is a needless assumption. 

 In the case of Citrus, where the branching vessels start from the 

 chalaza, they ramify in the tegmen, or inner coat, as this is only 

 organically continuous with the outer tunic and raphe at that 

 point. 



April 3ril, 1858. 



XXXIV. — Further Observations on the Nature and Origin of the 

 External Coatings of Seeds. By John Miers, F.U.S., F.L.S. 

 &c. 



The arguments which 1 lately offered, relative to " the natm-e 

 and origin of the external coatings of seeds," are founded prin- 

 cipally upon the facts recorded by the most eminent ])hysio- 

 logical botanists, who have described and figured the gradual 



