348 



SCIENCE. 



[N. S. Vol. III. No. 62. 



tration, of Giard . This is known in Lychnsi 

 dioica, Saponaria officinalis, Dianthus sin- 

 ensis, Knautia arvensis and Scabiosa suc- 

 cisa. Parasitic castration arises from the 

 substitution of sterile cells or fungal spores 

 for the ordinarily present pollen-mother 

 cells of the stamens. It is distinguished as 

 indirect parasitic castration, by Giard, from 

 the case of Claviceps growing as a substitu- 

 tionary form and quite destroying the ovary 

 of the rye, where the pseudomorph is said 

 to produce direct parasitic castration. 



Flowers attacked by aphides show the 

 following characters: 



1. Complete chlorosis in which all the or- 

 gans of the flower assume the external and 

 internal characters of foliage leaves (Phyl- 

 lody), example, Sinapis and Torilis. 



2. Complete chlorosis with hypertrophy, 

 but the resultant structures differing from 

 foliage leaves (Aphyllody), example, Cer- 

 astium, Silene, Valerianella. 



The most marked characteristic of flowers 

 converted into cecidia by gall flies is a neg- 

 ative one, viz: the generally slight structu- 

 ral change that they undergo. Hypertrophy 

 is the principal reaction — seen well in flow- 

 ers of Raphanus, Sisymbrium, Lotus and 

 Daucus. The flowers of Veronica and Cer- 

 astium are. however, not particularly en- 

 larged, but become concealed in a mass of 

 cecidial leaves. The fly-cecidia of Lychnis 

 and Scabiosa are distinguished by the for- 

 mations of numerous hairs, while those of 

 Tanacetum and Spiraea are remarkable for 

 the general substitution of sclerenchyma 

 for parenchyma and might be classed as 

 sclerotoceeidia. 



Phytoptus galls are chiefly remarkable 

 for the cytic changes which take place in 

 them. Epidermal and hj^podermal cells 

 partake in the modification. The cyto- 

 plasm becomes highly granular, the nucleus 

 acquires large dimensions and is highly 

 chromatophilic. The formation of epidermal 

 hairs is abundant and numerous modifica- 



tions of the cell contents (chlorophyll, cal- 

 cium oxylate, etc.) are noteworthy. Doub- 

 ling, chlorosis, antholysis, atrophy and hy- 

 pertrophy characterize special cases. On 

 the whole, the Phytoptus galls in floral re- 

 gions are comparable best with the Aphis 

 galls, though differing in the greater stimu- 

 lation of epidermal tracts, and the conspic- 

 uous formation of hairs which, in Stachys 

 betonica,. are even produced in the embryo- 

 sac. 



Molliard's general conclusions may be 

 readily condensed into a tabular form, as 

 follows : 



I. Modifications undergone by accessory parts of 

 the flower. 



A. Modifications of organs. 



1. Accessory parts wither. 



2. Accessory parts undergo metamorphosis 



without hj'pertrophy. 



a. Phyllodic metamorphosis. 



b. Aphyllodic metamorphosis. 



3. Accessory parts hypertrophy. 



a. Total hypertrophy. 



b. Partial hypertrophy. 



B. Modifications of tissues. 



1. Simple modifications, e. g., change in size of 



parenchyma cells. 



2. Modification of cell arrangement. 



3. Disappearance of tissues. 



4. Appearance of new tissues. 



5. Translooalization of characteristic cell con- 



tents. 



II. Modifications undergone by essential organs of 

 the flower. 



1. No modification, e. ff. Sherardia. 



2. Inhibition of flowers. 



3. Development of essential organs, but flower 



fails to open. 



4. Modification of sporangial areas, so that 



sterile cells are substituted for spores. 

 ( Parasitic castration ) . 



a. Castration of pollen sacs. 



1. Direct castration. Pollen cells digested. 



2. Indirect castration. Pollen cells meta- 



morphosed. 



b. Castration of ovules. 



1. Direct castration. Ovules digested. 



2. Indirect castration, where either the em- 

 bryo sac fails to develop or the egg nucleus of the em- 

 bryo sac fails to appear (inhibition of germination). 

 Molliard did not, however, discover a conversion of em- 



