f>06 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Lacistemacese. The result confirms the conclusion reached by Hof- 

 meister, Strasburger, and Hegelmaier, that the structure and mode of 

 development of the megaspore and gametophyte of the Angiosperms is 

 not a satisfactory index of genetic relationship, since these features may 

 vary very widely even within the limits of a single family or genus. 

 Thus among the Piperacere, Piper has a typical embryo-sac with typically 

 developed endosperm, and the closely related genus HecTceria is prac- 

 tically identical in these respects. Peperomia, as well known, shows a 

 most remarkable deviation in the development of the embryo-sac. In 

 all of these Piperaceae only one megaspore is formed, and the tapetum 

 is persistent even to the ripe seed. But in the Saururacese, the functional 

 megaspore is one out of two potential megaspores in Anemiopsis, and 

 one out of three in Houttuynia and Saururus. A tapetum is absent in 

 Houttuynia, though formed and persistent in the other two genera. 

 The embryo-sac is typically seven-nucleate, but the first division of the 

 endosperm nucleus is followed by a cell-wall cutting the sac into an 

 upper and a lower cell, only one of which, the upper, divides further to 

 form a considerable mass of endosperm, the lower cell forming an 

 elongated haustorium. 



In Lacistema, a single archesporial cell gives rise to three potential 

 megaspores, one of which forms a typical embryo-sac with endosperm 

 formed at first by free-cell formation. Hedyosmum (Chloranthaceaj) 

 differs in that the endosperm is cellular from the first. The author 

 points out that we have here among a few genera a variety nearly as 

 great as can be found in the whole group of Angiosperms. The facts 

 noted supply no important evidence for or against the affiliation of the 

 Chloranthaceae and Lacistemaceas with the Piperales. But the complete 

 replacement of the nucellar tissue by endosperm in Hedyosmum and 

 Lacistema, and their well-developed embryo, show a marked contrast 

 with the abundant perisperm, slight endosperm, and small embryo of the 

 Piperaceae and Saururacese. 



Physiology. 

 Nutrition and Growth. 



Development of Root-Hairs.* — L. M. Snow gives the results of her 

 experiments on the causes of production of root-hairs. Light and 

 darkness have apparently only an indirect effect through their influence 

 on growth. High temperature with sufficient moisture tended to de- 

 crease hair production by increasing the elongation of the internal cells. 

 The slower the rate of growth in air, the better is the development of 

 the root-hairs. Retardation of growth by glass tubes, by wounding or 

 by resistance of the substratum, favoured hair production. Saturated 

 air at high temperature tended to suppress hair development, and a 

 similar result obtained with saturated soil in corn and wheat. Less hair 

 was developed in distilled than in tap water. Air deprived of oxygen 

 stopped the development of hairs and also retarded growth. The activity 



* Bot. Gazette, xl. (1905) pp. 12-48 (1 pi.). 



