24 SCIENCE PROGRESS 



lines. The features studied were the number, of root 

 poles, of primary double bundles, of intercalary bundles, of 

 bundles in the mid-region of the epicotyl and hypocotyl. 

 In dimerous seedlings the root is normally tetrarch, and 

 in trimerous hexarch, whilst the epicotyl typically contains 

 twelve bundles in the dimerous seedlings, and fourteen to 

 eighteen in the trimerous ones. This variation in the latter 

 case is due to failure of one or more of the nine primary epi- 

 cotylar bundles (six in normal seedlings) to divide. Additional 

 intercalary bundles (o to 6) may appear, especially in the normal 

 type, as a consequence of division of the hypocotyl strands. 

 The coefficient of variation for the intercalary strands was 

 182*7 for the normal, and 274*92 for the trimerous seedlings. 



In the hypocotyl the variability of bundle number is much 

 higher in the dimerous seedlings than in the trimerous, but the 

 reverse is true for the epicotyl. In the latter the number for 

 dimerous seedlings ranged from ten to sixteen, and for the 

 trimerous from twelve to twenty-two. Statistical constants 

 are furnished for all the data which serve to emphasise the 

 necessity for such methods before drawing any theoretical 

 conclusions. 



Economic. — M. Forbin in La Nature describes the new rubber 

 industry of Mexico, the source of which is the guayule {Par- 

 ihenium argentatum) : this plant covers an exploitable desert 

 area of about 70,000 sq. kilometres, at altitudes of from i ,000 

 to 2,000 metres. Its demands on the soil appear to be very 

 slight, provided there is a certain proportion of calcium present. 

 The rubber is obtained by maceration in water, and the yield is 

 about 12 per cent, by weight and of excellent quality. A 

 number of factories are now engaged in its exploitation, and the 

 plant may well prove a valuable asset in other desert regions. 



Taxonomy. — Col. Godfery describes two new orchid hybrids, 

 in the Journal of Botany for March, One from Italy, between 

 Serapias Lingua and Anacamptis pyram,idalis , the second from 

 France, between Ophrys arachnitiformis and O. scolopax. In 

 the same Journal for April Col. Godfery describes Epipactis 

 Muelleri, sp. no v. A new variety of Stachys sylvatica is 

 described by Mr. Cutting, and in the same number Miss Lister 

 describes and figures three new species of Mycetozoa, one of which 

 is placed in a new genus, Minakatella, found in Japan. The 

 other two species are British, Physarum ovisporum and Arcyria 

 carnea. 



Ecology. — Our knowledge of the water relations of the 

 soil in relation to plant growth is comparatively meagre, despite 

 the large amount of experimental work on wilting coefficients, 

 etc. Recently Bouyoucos (Soil Science Jour.) has investi- 

 gated the nature of the water in soils by means of the dilato- 



