Botany 119 



sulphates, iron, and calcium compounds has been determined and some important 

 facts bearing upon the changes in woody tissue probably initial to the formation 

 of coal have been obtained. Prof. J. C. Jones, of the University of Nevada, has 

 made brief studies of the travertine coatings found on the solid granite near the 

 level of the highest beach line, establishing the participation of biological agencies 

 in their formation. Mr. S. B. Parish, of San Bernardino, has written a descrip- 

 tion of the plants which form the vegetative setting of the drama of the appear- 

 ance and disappearance of the lake. Dr. MacDougal has devoted attention chiefly 

 to the revegetation of the areas laid bare by the desiccation of the lake in which 

 about sixty species have participated. Important contributions have been made to the 

 subjects of dissemination by birds, winds, and by flotation of seeds and seedlings. 

 The re-occupation of sterilized islands has been followed, and the efficiency of 

 various agencies in distribution evaluated. 



No. 297. MACDOUGAL, DANIEL T. Hydration and Growth. Octavo. In press. 

 The purpose of the investigations described in this work was to ascertain the 

 forces outside of osmosis, which are concerned in the mechanism of growth. 

 Auxesis or actual increase of the mass of living matter consists in the accretion 

 of new molecules of solid matter and their hydration or combination of molecules 

 of water. The assumption has prevailed hitherto that all protoplasm was pre- 

 dominantly proteinaceous and that growth consisted chiefly in the increased hy- 

 dration or swelling which followed the action of the hydrogen on such am- 

 photeric substances. Substantial foundation has been found, however, for the 

 conception that in the plant cell soluble and readily diffusible sugars (polysac- 

 charids) pass into the growing cells where a large proportion is converted into 

 the non-diffusible or mucilaginous pentosans. These pentosans have a relatively 

 large hydration capacity, which is reduced by the hydrogen ion, but which is in- 

 creased by amino compounds, such as asparagin, glycocoll alanin, and phenyldarrin. 



Biocolloids were made up from agar, tragacanth, acacia, and cherry gum as 

 representing the carbohydrates and of gelatin and plant albumins representing the 

 proteins. Measurement of the action of dried plates of such material estab- 

 lished striking similarities with dried and living sections of plants. The general- 

 izations thus obtained were used in the interpretation of the growth phenomena 

 of such organs and members as joints of cacti, sunflower stems, wheat seedlings 

 leaves, pods, fleshy fruits, and tree stems. The action of temperature, water- 

 loss, and varying acidity of the sap in causing variations in the rate and amount 

 of growth was measured. 



The origination of succulence in plants and the cause of the xerophytic habit 

 and spirose form of desert species is attributed to the dehydration of sugars 

 with their resultant conversion into mucilages in one case, and in the other the 

 formation of wall material is accelerated with an accompanying restriction in 

 growth. The technique of preparation and measurement of the swelling of biocol- 

 loids by the auxograph is described. The same instrument is used in obtaining 

 growth records and variations in volume of plants. 



No. 117. CANNON, W. A. Studies in Heredity as Illustrated by the Trichomes of 



Species and Hybrids of Jnglans, Oenothera, Palaver, and Solatium. 



Octavo, m-f-67 pages, 10 plates, 20 figures. Published 1909. Price $0.75. 



A cytological study of the origin, development, variations, and inheritance of the 



hairs of several plants, chiefly for the purpose of determining whether or not the 



hairs or systems of hairs borne by a plant might be considered as unit characters. 



When two plants were hybridized which bore the same types of hairs but of different 



dimensions, the hybrid resulting showed intermediate organs, but a distinct type 



borne by either parent was transmitted unchanged, or as an indivisible unit character. 



No. 131. CANNON, W. A. The Root Habits of Desert Plants. Octavo, 95 pages, 



23 plates, 17 text figures. Published 1911. Price $1.50. 



The results of a study of the root habits of representatives of the principal types 

 of desert species are given in detail in this contribution. Among these forms it is 

 found that the general aspect of the root-system is characteristic and that like the 



