ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 445 



Anatomy of the Euphorbiacese.* — L. Gaucher has investigated 

 375 species, representing 126 genera and all the tribes except Kicino- 

 dendrinese. He concludes that there is, in spite of the extent of the 

 family, its wide distribution, and its polymorphism, an aggregate of 

 anatomical characters sufficiently constant to define the Euphorbiaceous 

 type. They are as follows : — In the stem the phellogen is sub-epi- 

 dermal, the pericycle forms in front of the vascular bundles fibrous 

 islands or masses of fibres, intermingled with sclerotic cells, the vascular 

 system forms a ring scarcely interrupted by medullary rays which are 

 composed of a single row of cells ; these cells are sclerotic in the region 

 of the wood ; the pith is also often sclerotic. Tannin sacs and calcium 

 oxalate (except in Euphorbia) occur in the stem, in cortex, pericycle, 

 phloem, and pith ; they are especially abundant in the bast rays, where 

 they mark very sharply the limit of the bundles. In the leaf the epi- 

 dermal cells have a very uniform structure. The cuticle is generally 

 quite plain, and the stomata are always ou a level with the epidermis, 

 and very rarely surrounded by subsidiary cells. As regards the sub- 

 division of the order, anatomical characters bear out the generally 

 recognised grouping. The PhyllanthoideaB are remarkable for the 

 presence of water-reservoirs formed by epidermal cells or cells imme- 

 diately below the epidermis. Laticiferous tissue and internal phloem 

 are absent. The Crotonoideae have no water-reservoirs, but often show 

 a well-developed hairiness. They have also laticiferous tissue and in- 

 ternal phloem. The Stenolobeze have laticiferous tissue, but no internal 

 phloem ; they approach the two other tribes in that some have a water- 

 storing apparatus, while others are hairy. 



The internal bast of the Crotonoideae occurs in four principal forms. 

 In the Euphorbia typo it forms a narrow zone around the pith, and 

 consists of elongated cells with brightly shining walls, but with no 

 trace of sieves. In the Tragia type it forms islands opposite the vascular 

 bundles. The cells resemble those of the Euphorbia type, but some of 

 the transverse walls, thicker and more refractive than others, are per- 

 forated in places. In the Groton type the phloem islands are more 

 extensive, and have true sieve-tubes. The type of Lepidoturus is 

 characterised by a girdle of sclerenchyma in addition to the phloem. 



The latex receptacles are unicellular or multicellular, and never 

 anastomose. The unicellular are sometimes surrounded by a sheath of 

 parenchymatous cells (reserve tissue), giving the appearance of a secre- 

 tory canal. The multicellular comprise two well-defined types. In 

 one a number of elongated cells is placed in series, which is more or 

 less regular according to the persistence or absorption of the transverse 

 cell- walls. In the second type a number of cells irregularly arranged 

 form by their union the latex-carrying tissue. Latex-carriers of very 

 different form occur in different parts of the same organ. The author 

 gives a table showing the distribution of the various forms in the 

 family. 



The latex-carriers pass from the stem into the leaf, where they 

 spread through the mesophyll and surround closely the assimilatory 

 tissue. The latex is for the most part composed of substances of a 

 high nutritive value, of the same nature as the contents of the reserve 



* Ann. Sci. Nat., ser. 8. xv. (1902) pp. 161-309 (81 figs.). 



