ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 805 



more and more evident that the life of all living organisms depends 

 on the vitality of this one and the same substance. 



Protoplasm of Compound Latieiferous Tubes.* — The presence 

 of protoplasm in latieiferous vessels was not detected by the older 

 botanists ; it has, however, been recognized in the compound latiei- 

 ferous tubes of the Euphorbiaccaa, TJrticacese, Apocynaceaa, and 

 Asclepiadea3. E. Schmidt now adds to this list the following orders : — 

 In the Cichoriaceaa, protoplasmic sac and nuclei were detected in 

 Scorzonera hispanica and species of Sonchus ; in Campanulaceae, in 

 Campanula ramosissima ; in Lobeliaceae, in Siphocampylos bicolor ; and 

 in Papaveraceje, in Palaver. In Chelidonium the coalescence of the 

 individual cells is imperfect ; and the protoplasmic sac and nucleus 

 could be made out in each separate cell. The same is the case with 

 Carica Papaya among Papayaceje. In Calndium marmoratum, among 

 AroideJB, similar results were obtained. The so-called latieiferous 

 tubes of Musaceas are regarded by the author as rows of superposed 

 tubes the contents of which are only locally in communication with 

 one another ; no nucleus or living protoplasmic sac could be detected 

 in them. In many cases, and especially in the Musaceae, it is very 

 easy to mistake the coagulated latex for true protoplasm. 



In all the plants observed which contained compound latieiferous 

 tubes, the protoplasm of the individual cells coalesces into a large 

 " symplast," which retains its optical and colouring properties to the 

 last without change. The nuclei also remain in the vessels after the 

 fusion of the cells without any alteration of form or structure till the 

 complete maturity of the organ. It is not probable that any division 

 of the nuclei takes place after the fusion. The vitality of the proto- 

 plasmic sac appears to be established by the following facts. In 

 many cases the fusion takes place before the organ has attained its 

 full size. If the mature vessels are injured, the protoplasm has also 

 the power of repairing the wound, as in the multinucleated Siphoneaa, 

 and in many pollen-tubes. This is effected by annular thickening 

 ridges on the wall of the tube, which finally completely close up the 

 wound, the substance of these thickenings being identical with that of 

 the callus of sieve-tubes. An additional proof of the vitality of the 

 protoplasm is that, after the growth of the wall of the vessel is com- 

 pleted, it increases in thickness over its whole surface ; and further, 

 in the living plant, the latex cannot be coagulated by contact with 

 water of imbibition. The latex, which is formed subsequently to the 

 fusion, can also be regarded only as the product of a living protoplasm 

 in the latieiferous vessels. 



Development of the Embryo-sac. f — As a sequel to his researches 

 on the embryo-sac of Leguminosae,! L. Guignard gives an historical 

 resume of our knowledge of the structure of this organ in various 

 natural families of plants, derived from his own observations and those 

 of others. The following is an epitome of the general results : — 



The embryo-sac never arises from the fusion of two cells, but 



* Bot. Ztg., xl. (1882) pp. 435-48, 451-66 (1 pi.). 



t Ann. Sci. Nat. (Bot.) xiii. (1882) pp. 136-99 (5 pi?.). 



X See this Journal, ante, p. 644. 



