676 SUMMARY OF CURRENT RESEARCHES RELATING TO 



or stem of the axis of the embryo. The primary radicle differs from 

 other roots only in the fact that its axis is continiious with that of the 

 stem ; it is also endogenous, although this is not very evident where 

 the suspensor is very slender. Primary and secondary roots differ 

 only in their position on the axis of the plant ; the term " tigellum" 

 {hypolcotyles Stengel glied) ouglit properly also to include the sus- 

 pensor. The embryo of Avicennia has (as described by Treub) no 

 root-cap, because it has no primary radicle ; but, on the other hand, 

 several endogenous secondary roots at the lower end of the tigellum, 

 as occm-s in Graminete, Trapa, Lnpatiens, &c. 



Cellulin, a modification of Cellulose.* — A further examination has 

 been carried out by N. Pringsheim of the peculiar granular bodies 

 lon« since observed by him in the fertilizing tubes and oogonia of the 

 Saprolegniefe, and described by Zopf as " amoebae." f They are 

 found in the fertilizing tubes at all ages. While young they are flat 

 disk-shaped or polyhedral plates with rounded corners, composed of 

 a dense homogeneous substance ; they vary greatly in size and form. 

 They gradually become stratified, and finally as completely and 

 regularly so as starch-grains. They are abundant also in the oogonia, 

 and a few grains occur in other parts of the plant. J 



The structure, mode of development, and chemical properties of 

 these substances, show that they are neither organs of reproduction 

 nor independent parasitic organisms, but are a sj)ecial modification of 

 the cell-contents. The stratification indicates a close resemblance to 

 other bodies of this character. They are, however, not coloured blue 

 by iodine ; nor do they take any other colour but that of the iodine 

 itself. They are completely insoluble in all ordinary solvents of oils 

 and resins, even in absolute alcohol and in ether. Nitric acid, either 

 with or without ammonia or j^otash, produces no effect on them, nor 

 does Millun's reagent. They have no power of taking up colouring 

 substances, except under special circumstances. Caustic alkalies 

 produce, in the cold, no visible effect on these bodies ; and very little 

 change is effected by dilute or concentrated nitric or hydrochloric 

 acid at the ordinary temperature. In moderately concentrated sul- 

 phui'ic acid they dissolve rapidly and completely at the ordinary 

 temperature, as also in solution of zinc chloride, when not too dilute. 

 They do not dissolve in ammoniacal copper oxide, even after long 

 treatment. 



These reactions show that the bodies in question belong neither to 

 the proteinaceous cell contents, nor to the series of oils and resins ; but 

 that they are composed of a substance closely allied to cellulose 

 which has been separated from the protoplasm in a granular form. 

 It is perhaps identical with so-called " fimgus-cellulose," and with 

 the " fibrose " of Fremy ; and Pringsheim proposes for it the term 

 cellulin. Its special chemical characteristic is its remarkable solu- 

 bility in dilute sulphuric acid and in an aqueous solution of zinc 

 chloride. 



* Ber. Deutsch. But. Gesellsch., i. (1883) pp. 288-308 (1 pi.), 

 t See this Juurual, ante, p. 248. 

 X Ibid., mfra, p. 687. 



