62 ■ REPORTS OF INVESTIGATIONS AND PROJECTS. 



Desert Soils and Soil-moisture. — Dr. Burton E. Livingston has continued 

 his observations on the principal soil formations of the regions about Tucson. 

 Especial attention has been given to the adobe clays of Tumamoc Hill, to the 

 shallow formation underlaid with caliche and bearing the creosote-bush, and 

 to the broad beds of sandy washes, as well as to those of the river flood-plains. 

 The march of the soil-moisture in these places has been followed and the 

 more important features in the variations estimated. The minimum amount 

 of water for plant activity is about 30 per cent. In the course of this work 

 Dr. Livingston has been able to devise a simple apparatus by which a porous 

 cup filled with water and buried in the soil may give a continuous record of 

 the amount of soil moisture present. 



The Plant Life of Maryland. — Dr. Forrest Shreve has been engaged since 

 his accession to the staff in the completion of his treatise embodying the result 

 of four seasons' field work carried on under the auspices of the State Weather 

 Service of Maryland. The distribution and associations of the vegetation 

 have been investigated in relation to the climate, geological features, soils, and 

 topography, and a list of the species compiled. The bringing of these freshly 

 accumulated facts into comparison with similar data from the desert has re- 

 sulted in some broader generalizations. 



Histological Studies on Hybrids.- — Tlie examination into the anatomy of 

 hybrids and their pure parents, which was carried on during the summers 

 of 1907 and 1908 by Dr. W. A. Cannon and mentioned in the Year Book of 

 1907, has been concluded. The investigation included the following forms : 

 Juglans calif ornica X Jnglans nigra, Jnglans calif ornica X Juglans regia, 

 Oenothera lamarckiana X OenotJiera cruciata, Papaver somnifernm X Pa- 

 paver orientale, Papaver somnifernm X Papaver pilosuui, and Solanuni vil- 

 iosum X Solamim guinensc. The observations were confined to the trich- 

 omes, whose embryonic and mature conditions were studied and compared. 

 Some of the conclusions may be presented in brief here ; an account of the 

 research will be given later in another place. 



In OenotJiera three types of trichomes were seen in the pure species and in 

 the second and third generations of the cross. Numerous measurements on 

 the length of the trichomes show that those of the hybrid are intermediate in 

 size, but not strictly so. The different types of trichomes behave in an inde- 

 pendent manner as regards their distribution, a circumstance that points to the 

 necessity, in studies on heredity, of analyzing their distribution in place of 

 grouping all types, as is the present custom. The Papaver hybrids were either 

 quite sterile, or only partly fertile ; the first generation alone was brought 

 under observation. Although the first generation of either hybrid was in gen- 

 eral appearance not intermediate, in certain structural characters this was the 



