ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 591 



of V. persica. This sucker is an energid with four (more rarely six) 

 nuclei, situated in the micropjlar cavity, and by absorption of tlie sur- 

 rounding tissues, growing down into the funicle. It behaves in a para- 

 sitic manner, and when completely developed surrounds the vascular 

 bundle of the funicle with its branches ; it then gives rise to the for- 

 mation of a confused mass of cellulose. Its duration is characterized 

 by two periods : (1) a period of zymogenic activity, when the chromatin 

 is very active ; (2) a period of decay, when the chromatin degenerates 

 and the nucleolus reaches its maximum activity, the substance of the 

 latter serving for the production of cellulose granules. 



Formation of Starch and Plastids in Plants.* — A Guilliermond 

 has studied the formation of chloroplasts and leucoplasts, and their rela- 

 tion to tlie manufacture of starch. He is able to confirm the opinion 

 expressed by Schimper and A. Meyer that starch is invariably formed in 

 either chloroplasts or leucoplasts. The plastids themselves result from 

 differentiation of mitochondria of the embryonic cells and of the cells 

 of the meristem ; the mitochondria occur in three forms : {ci) minute 

 grains ; {h) chains of granules ; (c) elongated and flexible filaments ; 

 leucoplasts are always derived directly from one or other of these forms, 

 chromoplasts usually in the same manner, more rarely by metamor- 

 phosis of the leucoplasts. From the histological and chemical point of 

 view, mitochondria and plastids are very similar, but the plastids are 

 specialized to perform a particular function. Mitochondria can only 

 multiply by division, and they are transmitted from the parent-plant to 

 the ^g^, and from the ^gg to the adult plant. The present study shows 

 the complete homology between the animal and plant-cell, especially in 

 regard to the process of secretion. 



" Myelinformen " and Chondriosomes.t — A. M. Lowschin has 

 studied the "Myelinformen," which give rise to the albumins of 

 lecithin. These bodies are of varied form, resembling short rods, 

 dumb-bells, threads, rosaries, etc. The form assumed depends upon 

 tlieir construction, surface-tension, the physico-chemical characters of 

 the surrounding medium, and their own condition of rest or movement ; 

 the thread-like forms or spermatozoid-shaped bodies are present where 

 there is a streaming movement. The soructure is similar to that of 

 chondriosomes ; they may be homogeneous or enclosed in a more or 

 less variable membrane. The size varies considerably and depends on 

 the quantity of material used, the fineness of division, and the characters 

 of the surrounding medium. A longitudinal splitting may sometimes 

 be detected. Their origin, development, and disappearance are in inti- 

 mate relation with their structure and the character of the surrounding 

 medium. Division occurs similar to that described for mitochondria. 

 They are very sensitive to the action of chemical reagents, and have a 

 fixed condition of equilibrium ; they can be fixed by formol, osmic acid, 

 and chromic acid, but pure water converts them into a uet-Hke mass ; 

 they are disorganized by acetic acid. Thus in size, form, structure, and 



* Arch. Anat. Micr., xiv. (1913) pp. 309-428. See also Eev. Gen. Bot., xxv. 

 (1913) pp. 271-2. t Ber. Deutsch. Bot. GeselL, xxxi. (1913) pp. 203-9. 



