448 



KNOWLEDGE. 



November, 1910. 



BOTANY. 



Bj' Professor F. Ca\'ers, D.Sc. F.L.S. 



AMMONIUM SALTS AND PLANT NUTRITION.— 

 .According to Prianischnikow (Ber. dcidsch. bot. Gcs., 1909), 

 the partial substitution of sodium nitrate by ammonium 

 sulphate in cultures increases the power of the plant to gain 

 phosphoric acid from raw phosphates. In the absence of 

 annnonium sulphate the plants (grasses were used in the 

 experiments) show phosphoric acid starvation, while total 

 substitution greatly reduces the harvest, and the best results 

 are obtained by replacing about one-half of the sodium nitrate 

 by ammonium sulphate. These effects are attributed to the 

 liberated sulphuric acid ; in partial substitution, the acid was 

 strong enough to aid in dissolving the raw phosphate, while in 

 total substitution it was so strong as to injure the plants 

 seriously. The consumption of phosphate was favoured, and 

 injury by ammonium sulphate pre%'ented, by adding carbonate 

 of lime. With barley, peas, and buckwheat, the author claims 

 that mixtures of sodium nitrate and ammonium sulphate are 

 better sources of nitrogen than either one alone, because the 

 former is physiologically basic and the latter physiologically 

 acid ; fhi' two together keep the culture mcdiiun neutral. 



THE HYDROGEN BAG TERI A. — Winogradski's 

 researches established the existence of non-chlorophyllous 

 plants that make their organic food by energy obtained from 

 the oxidation of various simple inorganic substances. Lebedeft 

 {Bcr. (h'litsch. bot. Ges., 19101 has made an extensive study 

 of the hydrogen bacteria, which oxidise hydrogen as the source 

 of energy for the assimilation of carbon dioxide. These 

 bacteria, it appears, are capable of using organic food as well, 

 and they are therefore distinguished from the nitrite, nitrate 

 and sulphur bacteria. The fixing of any given volume of 

 carbon dioxide requires the oxidation of from five to fifteen 

 volumes of hydrogen. The oxygen required for the process is 

 best obtained from .atmospheric oxygen, but in absence of it, 

 nitrates can be decomposed as the source of oxygen. 1 he 

 oxidation of hydrogen still continues in the presence of organic 

 food, l)ut no carbon dioxide is fixed in that case. 



SOME RECENT WORK ON SELAGINIXLA.— A very 

 small xerophytic species of SclagiiicUa — -S. prcissiaiia — has 

 been described by Bruchmann [Flora. 19101. In this curious 

 little plant, which grows in West Australia, Victoria, and 

 Tasmania, the cotyledons are larger than the foliage-leaves ; 

 the first branching of the young plant gives off an erect shoot 

 a little over an inch high, the other branch becoming the 

 creeping rhizome, which then gives off erect branches right 

 and left. The stem is protostelic ; in the young stem 

 (hypocotyl) there is a single exarch protoxylem, hence the 

 structure is very simple. The roots have no root-hairs, but 

 are infested by an endophytic fungus; the hyphae wcmc 

 observed penetrating the epidermis from the soil. 



Miss Mitchell (.4)(/;. Bot.. 19101 has recorded \'arious 

 observations on the cone of Selagiiiclla. The axis may 

 renew its ordinary vegetative growth beyond the sporangia ; a 

 second cone may be produced on such an axis, the two cones, 

 or fertile regions, being separated by a sterile region ; the 

 cone may undergo branching. The distribution of sporangia 

 is variable, and in different species we may get ( 1 ) one large 

 basal megasporangium, (2) several basal megasporangia. 

 succeeded by niicrosporangia. 13) cones with numerous 

 microsporangia only. (4) cones with numerous megasporangia 

 only. (51 an indeterminate arrangement. Then, there are 

 species with one, two, or three megaspores in each megaspor- 

 angium, instead of the usual four ; also, two rare cases in 

 which there are eight (S. iiivolvens), and twelve (S. vogelii) 

 megaspores. 



Our knowledge of SclaiJiiiclla. familiar to students and 

 teachers as a botanical " type," has been greatly extended 

 during the last few years, especially by the remarkable 

 observations of Lyon, who showed that in some species the 

 megaspore germinates, producing the prothallus and 

 archegonia, in situ in the sporangium, which opens and lets in 

 the antliero^oids, so that we get practically a seed formed. 



Lyon showed also that in some species the embryo is formed 

 directly from the fertilised egg cell, without the development 

 of a suspensor. 



ACTION OF MANGANESE ON PLANTS.— One of the 

 very few definite examples, so far discovered, of localised 

 action produced by absorption of a specific chemical element 

 by a plant, has recently been noted by Molisch iSitz. kiiis. 

 Ak. Wiss., Vienna). It was found that the introduction of 

 manganese salts into water containing submerged aquatics — 

 Elodea. VaUisiteria. Water Milfoil, Water Crowfoot — 

 produced, after exposure to light for a few days, a deposit of 

 brown substance in the walls of the epidermis cells, which 

 soon increased so much as to mask the green colour of the 

 leaves. 



SOME RECENT W( )KK ON FOSSIL GVMNOSPERMS. 

 — Bit bv bit, our knowledge of the lower seed-plants is 

 increasing, and the gaps between already known forms are 

 being gradually filled up. 



Scott and Maslen (Ann. Hot., 1910) have described a new 

 genus (Mesoxylon) of Cordaitales, from the Lower Coal- 

 Measures of Lancashire. This genus is intermediate between 

 Cordiates and Poro.xylon, resembling the former in general 

 anatoms' — especially in the large pith — and the latter in 

 having centripetal xylem. The wood is dense, with narrow 

 ravs and small tracheids. It is regarded as completely 

 bridging the gap, so far as anatomy is concerned, between the 

 Poroxyleae and the Cordaiteae. 



Nathorst (Handl. K. Sv. Vet. AI;.. 1910) has described 

 the reproductive structures of several Bennettitales. He found 

 both microsporangia (with spores) and seeds in three species 

 of Williain.'ionia. from the Jurassic of Whitby and Scar- 

 borough. In a new genus, Wielandiella. a remarkable 

 vegetati\e structure is described — the stem, which is very 

 slender, branches freely in an apparently dichotomous manner ; 

 in the cones, which occur in the forkings, there are remains of 

 both pollen and seeds, k third genus, Cycadocephalus. has 

 pollen-grains with remarkably close resemblance to fern spores. 

 Nathorst also describes two cones from the Rhaetic of Sweden, 

 in which the seeds apparently had an aril like that of the Yew. 

 In Palissya, the ovuliferous cone scales bear two rows of 

 seeds : while Stachyta.xus has Yew-hke foliage, and attached 

 to the ends of the twigs are loose cones with distant scales, 

 each of w-hich bears two ovules. 



Gothien iHandl. K. Sv. Vet. Ak.). describes \arious t\pes 

 of fossil wood from the Jurassic of King Karl's Land. In 

 Cedroxylon transiens. the wood shows the fitting character- 

 istic of Araucarineae. together with the ray structure of 

 Abietineae. 



Of greater general interest are the remarkable results 

 obtained by Hollick and Jeffrey [Mem. 'New York Bot. 

 Garden. 1909), from a study of the plant remains in Cretaceous 

 clays of Staten Island. The Conifers include three genera of 

 Abietineae [Pinns, Prepinus, Pityoxylon), of which the 

 species of Pinns are more archaic than any living species, 

 while Prepinus is still more primitive. The most important 

 result, however, is the discovery of no less than sixteen genera 

 of Araucarineae, of which nine are new. These Araucarians 

 include tvpes which had previously been referred to other 

 families of Coniferae (Taxodineae, Cupressineae, and so on). 

 from the general appearance of their leafy twigs. The authors 

 believe that the Araucarians of to-day have come from 

 .•\bietineous ancestors, through a group represented by those 

 Cretaceous Conifers which connect .Araucarineae with 

 .Abietineae. Thev also bring forward e\idence for the great 

 age of the pine-like Abietineae, and urge that the Conifers 

 have, Uke the Horsetails and Clubmosses, undergone extensive 

 reduction, those now living representing the degenerate 

 survivors of a once great race. 



That the Araucarians are very sharply distinguished from 

 all the other Conifers is further emphasized by the results 

 obtained by various workers on living types. It would seem, 

 in fact, that great modifications will have to be made in the 

 views that have generally been accepted as to the inter- 

 relationships of the Conifer group, which apparently forms a 



