and in other parts of the order Leguminosm. 261 



the size, and by no means readily distinguishable. In the black bryony 

 (Plate XLIV., Fig. 7) they are beautiful and large, about TsVijth 

 of an inch in diameter, thickly set at regular distances throughout 

 the testa. And as this plant, like other Dioscoreaceae, abounds in 

 true raphides, it affords a good instance of their occurrence with 

 ■ other saline crystals in the very same species. So, too, raphides and 

 long crystal prisms may occur in single plants of certain Pontederacess 

 and Liliaceae ; and the short prismatic crystals (Plate XLIV., Figs. 1, 

 2, and 3) in the fruit of Geraniaceae are very different forms from the 

 sphaeraphides which are so common in the calyx of the same order. 

 Many similar examples to the same effect are recorded in my former 

 memoirs on plant-crystals. 



It is hoped that this communication may induce microscopical 

 observers, both neophytes and experts, to pay some attention to a 

 branch of phytotomy which has been too much neglected. The 

 pursuit might prove pleasing and instructive, as well to those who 

 are so frequently inquiring for " good microscopic materials," as to 

 botanists with the higher aim of expounding the life-history and 

 natural characters of the manifold members of the vegetable 

 kingdom. 



Sect. II. — Ceystals in Leguminos^.* 



Name of the Crystals. — As they mostly belong to one or more 

 of the prismatic systems, and are seldom twice the length of their 

 breadth, we may provisionally call them short prismatic crystals, 

 some specific term being needful to distinguish them from raphides, 

 and from the other long or acicular forms which I have always 

 called crystal prisms. It should be borne in mind that raphides, 

 regularly having rounded shafts and tips, have not the figure of 

 prisms ; that the long crystal prisms, on the contrary, though often 

 as thin as raphides, have distinct faces and angles; and that the 

 objects now to be described under the name of short prismatic 

 crystals are very different in shape from either raphides, long crystal 

 prisms, or sphaeraphides. 



How to find the Short Prismatic Crystals. — This may be done 

 after the manner recommended in Sect. I. Of Leguminous plants 

 the novice may commence his examinations in the leaves of the 

 common white or Dutch clover, or of Mimosa pudiea, and the 

 young pods of the garden pea [Pisum sativum) ; taking care to look 

 especially at the fibro-vascular bundles, alongside of which the crystals 

 occur abundantly in strings of cells. To facilitate their exposure 

 those bundles may be dissected from the surrounding parts, and then 

 cut or scraped into thin shavings, or mashed into fragments, in a drop 



* The substance of this section was orally communicated, with drawings, and 

 extemporaneous demonstrations in the fresh plants, to the East Kent Natural 

 History Society, Oct. 2, 1873. 



X 2 



