478 KECOKD OF SCIENCE FOK 1887 AND 1888. 



not a necessary coustituent. He gives C28H47K3O6 as the formala for 

 I)hyllocyanic acid. Schuuck has also studied the chemistry of chloro- 

 phyle (Proc. llo3^ Soc. Lond., xlii). Hansen states (Arbeit. lust., 

 Wiirzburg, in) that the orauge-red pigment reported to have been 

 observed in leaves is only an aggregation of the yellow chlorophyll 

 pigmeut, which has an orauge tint when present in dense masses. Epi- 

 dermal chlorophyll has beeu farther studied by Moore (Jouru. Bot., 

 XXV) aud the preparation of pure chlorophyll described by Macchiati 

 (Malpighia, i), Peyrou (Conipt. Eend., cv), has devised an instrnmeut 

 with which he has investigated the hourly variation in the action of 

 chlorophyll, finding that the function at diftereut houi^s in the day is 

 proportional to the intensity of light. 



Numerous other cell-contents have been studied. Hillhouse (Midi. 

 Nat., X aud xi) has investigated the function of tannin, and finds that 

 it is not used in the process of growth after its production, and it can 

 not therefore be regarded as a food material. Fribosin is described by 

 Zopf (Ber. deutsch. Bot. Gesell., v) as a new cell-content, found in the 

 couidia of Podosphcera, SpJuerotheca and Erysiplie. The formation of 

 oxalate of lime in leaves has been investigated by Schimper(Bot. Zeit., 

 XLVi), aud the formation of calcium oxalate by Wakker (see Bot. Cen- 

 tralbl., xxxiv). In regard to the acid secretion from the roots of plants 

 Molisch states (Sitzb. K. K. Zool. Bot. Gesell., Wien, xxxvii), that it 

 attacks organic substances even more powerfully than inorganic, and 

 not only dissolves them but induces other important chemical changes. 



The use of histological elements as a means of classification has been 

 further investigated during the year, and while no comi^rehensive dic- 

 tum can yet be laid down, substantial progress has beeu made, ai.d the 

 prospect is that when all plants have been thoroughly investigated 

 distinctive characters will be detected. Hildebrandt, for example, has 

 examined a large number of species of Ambrosiece and Senecionidem 

 (Beitr. Z. vergleich. Auat. der Ambros. u. Senec. Inaug. Diss.) and con- 

 cludes that they may be very clearly distinguished by the histological 

 elements. Jiiunicke (Bot.Ceutralbl.,xxxi) also concludes that the three 

 genera of the Geraniace(V examined by him can be distinguished from one 

 auother by characters derived from the structure and distribution of the 

 vascular bundles in the leaf and flower-stalks. Juel (Bot. Ceutralbl., 

 xxxiii) has studied the anatomical structure of the Marcgraviacece, and 

 Solereder (see Bot. Ceutralbl., xxxiii) has discussed "The systematic 

 value of the perforation in the walls of vessels," and Wible has a paper 

 " Zur Diagnostic des couiferen Holzer," On the other hand, Plitt (Beitr. 

 z. vergleich. Auat. d. Blattstieles d. Dikotyledouen) has examined the 

 petiole or leaf-stalk of two hundred and eighty-three plants in thirty 

 natural orders for characters of systematic value and the results were 

 mainly negative, and Saupe (Flora, Lxx) has investigated the wood of 

 Leffiiminosea', and finds that the division into the suborders Papilion- 

 ac(c Cesalpinieie and Mimof^eiv does iu)t correspond to structural differ- 



