Varietäten, Descendenz, Hybriden. 197 



into vegetative rosettes, under highly favourable conditions of nu- 

 triment, is cited as an example of the essential similarity in the 

 behaviour of Sempervivum with that of the Algae and Fungi under 

 corresponding conditions. A sketch is given of Prof. Klebs' experi- 

 ments which resulted in the replacing of flowers bj^ leafy rosettes, 

 as v^ell as those in which striking modifications of the flowers 

 take place. 



For investigations upon the transmission of the altered charac- 

 ters to the posterity, Sempervivum aciiminatum was used. Highlj'' 

 altered flowers. with stamens transformed into petals were self- 

 fertilized. Out of 21 seedlings, 4 showed marked deviation from the 

 normal type in the characters of the inflorescence and flowers. The 

 deviations corresponded with those artilically produced in the mother 

 plant, and were developed without the use of the special methods 

 of culture necessary for the production of such forms in the mother 

 plant. R. P. Gregory. 



Mac Dougal, D. T., Influence of aridity upon the evolutio- 

 nary development of plants. (Plant World. XII. p. 217 — 231. 

 Oct. 1909.) 



A speculative consideration of the conditions under which the 

 origin and early evolution of life took place, and the eff"ect of water 

 dimnnition or aridity upon the broad features of plant evolution 

 and the development of desert floras. Plants with independent 

 gametophytes necessarily remained "with one foot in the water" 

 because water was an essential for accomplishing their fertilization. 

 The Problem of living away from water was solved, not by adapta- 

 tion of the gametophyte, but by the evolution of the sporophyte 

 with its highly complex Organization. Geological changes in climate 

 exerted their influence chiefly through their dessication effects. 

 Decrease of rainfall, leading to desert conditions, will exert a 

 variety of complex influences upon the Vegetation of a region. 

 There will be 1) localization of surviving species, 2) restriction of 

 seasonal activities. Two types of Vegetation will finally result from 

 desert conditions, l) forms with reduced leaf surface, i.e. spring 

 and switch-like perennials, and 2) forms which, in addition, have 

 developed the storage function. Such forms as the cacti, euphorbias, 

 agaves and yuccas are thus considered to be desert forms par 

 excellence. The effects of the reverse process, i.e. progressively 

 increasing humidity, in modifying a desert flore are also considered. 



Gates. 



Price, H. L. and A. W. Tr. Drinkard. Inheritance in Tomato 

 hybrids. (Bull. 177. Virg. Agric. Exp. St. p. 16— 53.5figs., lOpl. 1908.) 



It is found that a large number of characters in tomato hybrids 

 show Mendelian behavior. Thirteen such character pairs were stu 

 died, including fruit-shape (round or pyriform, two-celled or many- 

 celled), fruit color (red or pink, red or yellow^ yellow skin or 

 transparent skin), fruit surface (smooth or pubescent), foliage (cut- 

 leaf or potato leaf, green or yellow, smooth or rugous), stature 

 (tall or dwarf). Inter- and intra- specific crosses gave similar results, 

 L. pimpinellifolhmi behaving like the varieties of L. esculentum. 

 Fruit shape is found to be associated with and perhaps partly 

 determined by corolla characters. In crossing pubescent fruit with 

 smooth there is a partial reversal of dominance. The F^ shows two 



