1 887] Comparative Chemistry of Higher and Lower Plants. 725 
correspond to the larger ash-percentage of younger, or for- 
mative, parts of the growing plants. Some of these lower groups, 
as the diatoms of the Algz and the vascular cryptogams,’ con- 
tain enormously large ash-percentages; in the Horse-Tail, 
Equisetum,? 60 per cent. alone of silicic acid. The Lycopodium 
in addition to 14 per cent. of silicic acid, contains 27 per cent. of 
alumina and 2.5 per cent. of manganese. Among comparatively 
lower plants the willow and‘poplar* are rich in ash-constituents ; 
the formers contains 1.53 per cent. of manganese. Members of 
the sedge order.and grasses contain large quantities of silica; 
the rice-hull, 98 per cent. Various species of apetalous plants 
on the same evolutionary plane with these groups also contain a 
large percentage of ash-constituents, as the Salicornia, Salsola, 
Chenopodium, and Atriplex, also the Sugar-Beet. 
I have stated what chemical elements are essential for the life 
of the lower, as well as the higher, plants; also those which may 
occur in certain plants; and I have spoken of the two general 
classes of compounds of which plants are built as the volatile 
and ash constituents. The four elements carbon, hydrogen, 
oxygen, and nitrogen enter into the composition of the first 
class of compounds, and the grouping of these elements with 
each other and to the ash-elements constitute what is called 
plant chemistry. : 
-As certain chemical elements are always present in plants, so 
Certain changes occur and compounds are found generally, more 
especially among the albuminous constituents. However, even 
this statement should be restricted to saying that the first chem- 
ical reactions between these elements are probably identical at 
the start, the subsequent compounds formed depending upon the 
evolutionary stage. 
The infinite variety of these compounds is only equalled by 
the numerous genera and species of the vegetable kingdom ; 
though certain compounds frequently occur, as starch, sugar, . 
MERK and other bodies, correlated in special groups of plants 
wW . 
and distinct properties. For example, the true 
* Die Pflanzensenstoffe, p. 323, W. Lange; Bil. Ver., xi. 822. 
* Ann. Chim. Phys., xi. 62, 208; Ann. Chim. Pharm., 77, 295. 
3 Flückiger, Pharmacognosie, Kamp; Ann. Chim. Pharm., 100, 300. 
* Durocher and Lalaguti, Liebig’s agric. Chemie, 8 Aufl. 371. 
5 E, Riechardt, Chem. pharm. Centralbl., 268, 567- 
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